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‎README.md

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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0053 |[Maximum Subarray](src/main/dart/g0001_0100/s0053_maximum_subarray)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Divide_and_Conquer, Big_O_Time_O(n)_Space_O(1) | 361 | 88.89
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#### Day 2 Array
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109110

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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0048 |[Rotate Image](src/main/dart/g0001_0100/s0048_rotate_image)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Math, Matrix, Big_O_Time_O(n^2)_Space_O(1) | 311 | 90.24
112114

113115
#### Day 4 Array
114116

@@ -134,6 +136,7 @@
134136

135137
| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
136138
|-|-|-|-|-|-
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| 0049 |[Group Anagrams](src/main/dart/g0001_0100/s0049_group_anagrams)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, String, Hash_Table, Sorting, Big_O_Time_O(n\*k_log_k)_Space_O(n) | 376 | 92.86
137140

138141
#### Day 9 String
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@@ -264,6 +267,7 @@
264267

265268
| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0046 |[Permutations](src/main/dart/g0001_0100/s0046_permutations)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Backtracking, Big_O_Time_O(n\*n!)_Space_O(n+n!) | 319 | 80.00
267271

268272
#### Day 12 Dynamic Programming
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335339

336340
| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
337341
|-|-|-|-|-|-
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| 0039 |[Combination Sum](src/main/dart/g0001_0100/s0039_combination_sum)| Medium | Top_100_Liked_Questions, Array, Backtracking, Big_O_Time_O(2^n)_Space_O(n+2^n) | 316 | 96.88
338343

339344
#### Day 11 Recursion Backtracking
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347352

348353
| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
349354
|-|-|-|-|-|-
355+
| 0055 |[Jump Game](src/main/dart/g0001_0100/s0055_jump_game)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Greedy, Big_O_Time_O(n)_Space_O(1) | 331 | 97.53
350356

351357
#### Day 13 Dynamic Programming
352358

353359
| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
354360
|-|-|-|-|-|-
361+
| 0045 |[Jump Game II](src/main/dart/g0001_0100/s0045_jump_game_ii)| Medium | Top_100_Liked_Questions, Array, Dynamic_Programming, Greedy, Big_O_Time_O(n)_Space_O(1) | 335 | 81.58
355362

356363
#### Day 14 Dynamic Programming
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@@ -582,11 +589,14 @@
582589

583590
| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
584591
|-|-|-|-|-|-
592+
| 0055 |[Jump Game](src/main/dart/g0001_0100/s0055_jump_game)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Greedy, Big_O_Time_O(n)_Space_O(1) | 331 | 97.53
593+
| 0045 |[Jump Game II](src/main/dart/g0001_0100/s0045_jump_game_ii)| Medium | Top_100_Liked_Questions, Array, Dynamic_Programming, Greedy, Big_O_Time_O(n)_Space_O(1) | 335 | 81.58
585594

586595
#### Day 5
587596

588597
| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
589598
|-|-|-|-|-|-
599+
| 0053 |[Maximum Subarray](src/main/dart/g0001_0100/s0053_maximum_subarray)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Divide_and_Conquer, Big_O_Time_O(n)_Space_O(1) | 361 | 88.89
590600

591601
#### Day 6
592602

@@ -607,6 +617,7 @@
607617

608618
| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0042 |[Trapping Rain Water](src/main/dart/g0001_0100/s0042_trapping_rain_water)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Two_Pointers, Stack, Monotonic_Stack, Big_O_Time_O(n)_Space_O(1) | 328 | 80.77
610621

611622
#### Day 10
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767778

768779
| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0048 |[Rotate Image](src/main/dart/g0001_0100/s0048_rotate_image)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Math, Matrix, Big_O_Time_O(n^2)_Space_O(1) | 311 | 90.24
770782

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#### Day 8
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787799

788800
| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0049 |[Group Anagrams](src/main/dart/g0001_0100/s0049_group_anagrams)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, String, Hash_Table, Sorting, Big_O_Time_O(n\*k_log_k)_Space_O(n) | 376 | 92.86
790803

791804
#### Day 12
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11411154

11421155
| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0039 |[Combination Sum](src/main/dart/g0001_0100/s0039_combination_sum)| Medium | Top_100_Liked_Questions, Array, Backtracking, Big_O_Time_O(2^n)_Space_O(n+2^n) | 316 | 96.88
1158+
| 0046 |[Permutations](src/main/dart/g0001_0100/s0046_permutations)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Backtracking, Big_O_Time_O(n\*n!)_Space_O(n+n!) | 319 | 80.00
11441159

11451160
### Udemy
11461161

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11581173
| 0003 |[Longest Substring Without Repeating Characters](src/main/dart/g0001_0100/s0003_longest_substring_without_repeating_characters)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Sliding_Window, Big_O_Time_O(n)_Space_O(1) | 336 | 99.68
11591174
| 0020 |[Valid Parentheses](src/main/dart/g0001_0100/s0020_valid_parentheses)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, String, Stack, Big_O_Time_O(n)_Space_O(n) | 298 | 95.87
11601175
| 0005 |[Longest Palindromic Substring](src/main/dart/g0001_0100/s0005_longest_palindromic_substring)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, String, Dynamic_Programming, Big_O_Time_O(n)_Space_O(n) | 297 | 97.22
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| 0049 |[Group Anagrams](src/main/dart/g0001_0100/s0049_group_anagrams)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, String, Hash_Table, Sorting, Big_O_Time_O(n\*k_log_k)_Space_O(n) | 376 | 92.86
11611177

11621178
#### Udemy Binary Search
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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0001 |[Two Sum](src/main/dart/g0001_0100/s0001_two_sum)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Big_O_Time_O(n)_Space_O(n), AI_can_be_used_to_solve_the_task | 305 | 99.57
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| 0055 |[Jump Game](src/main/dart/g0001_0100/s0055_jump_game)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Greedy, Big_O_Time_O(n)_Space_O(1) | 331 | 97.53
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| 0041 |[First Missing Positive](src/main/dart/g0001_0100/s0041_first_missing_positive)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Big_O_Time_O(n)_Space_O(n) | 355 | 85.19
11731191

11741192
#### Udemy Two Pointers
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11761194
| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0042 |[Trapping Rain Water](src/main/dart/g0001_0100/s0042_trapping_rain_water)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Two_Pointers, Stack, Monotonic_Stack, Big_O_Time_O(n)_Space_O(1) | 328 | 80.77
11781197
| 0015 |[3Sum](src/main/dart/g0001_0100/s0015_3sum)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Sorting, Two_Pointers, Big_O_Time_O(n\*log(n))_Space_O(n^2) | 370 | 100.00
11791198

11801199
#### Udemy Famous Algorithm
11811200

11821201
| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0053 |[Maximum Subarray](src/main/dart/g0001_0100/s0053_maximum_subarray)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Divide_and_Conquer, Big_O_Time_O(n)_Space_O(1) | 361 | 88.89
11841204

11851205
#### Udemy Sorting Algorithms
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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0048 |[Rotate Image](src/main/dart/g0001_0100/s0048_rotate_image)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Math, Matrix, Big_O_Time_O(n^2)_Space_O(1) | 311 | 90.24
11941215

11951216
#### Udemy Linked List
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| <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
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|-|-|-|-|-|-
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| 0022 |[Generate Parentheses](src/main/dart/g0001_0100/s0022_generate_parentheses)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, String, Dynamic_Programming, Backtracking, Big_O_Time_O(2^n)_Space_O(n) | 312 | 79.37
1250+
| 0039 |[Combination Sum](src/main/dart/g0001_0100/s0039_combination_sum)| Medium | Top_100_Liked_Questions, Array, Backtracking, Big_O_Time_O(2^n)_Space_O(n+2^n) | 316 | 96.88
12291251
| 0017 |[Letter Combinations of a Phone Number](src/main/dart/g0001_0100/s0017_letter_combinations_of_a_phone_number)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, String, Hash_Table, Backtracking, Big_O_Time_O(4^n)_Space_O(n) | 293 | 92.50
1252+
| 0046 |[Permutations](src/main/dart/g0001_0100/s0046_permutations)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Backtracking, Big_O_Time_O(n\*n!)_Space_O(n+n!) | 319 | 80.00
12301253

12311254
#### Udemy Bit Manipulation
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12431266
| # | Title | Difficulty | Tag | Time, ms | Time, %
12441267
|------|----------------|-------------|-------------|----------|--------
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| 0055 |[Jump Game](src/main/dart/g0001_0100/s0055_jump_game)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Greedy, Algorithm_II_Day_12_Dynamic_Programming, Dynamic_Programming_I_Day_4, Udemy_Arrays, Big_O_Time_O(n)_Space_O(1) | 331 | 97.53
1269+
| 0053 |[Maximum Subarray](src/main/dart/g0001_0100/s0053_maximum_subarray)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Divide_and_Conquer, Data_Structure_I_Day_1_Array, Dynamic_Programming_I_Day_5, Udemy_Famous_Algorithm, Big_O_Time_O(n)_Space_O(1) | 361 | 88.89
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| 0051 |[N-Queens](src/main/dart/g0001_0100/s0051_n_queens)| Hard | Top_100_Liked_Questions, Array, Backtracking, Big_O_Time_O(N!)_Space_O(N) | 328 | 86.67
1271+
| 0049 |[Group Anagrams](src/main/dart/g0001_0100/s0049_group_anagrams)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, String, Hash_Table, Sorting, Data_Structure_II_Day_8_String, Programming_Skills_II_Day_11, Udemy_Strings, Big_O_Time_O(n\*k_log_k)_Space_O(n) | 376 | 92.86
1272+
| 0048 |[Rotate Image](src/main/dart/g0001_0100/s0048_rotate_image)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Math, Matrix, Data_Structure_II_Day_3_Array, Programming_Skills_II_Day_7, Udemy_2D_Arrays/Matrix, Big_O_Time_O(n^2)_Space_O(1) | 311 | 90.24
1273+
| 0046 |[Permutations](src/main/dart/g0001_0100/s0046_permutations)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Backtracking, Algorithm_I_Day_11_Recursion_Backtracking, Level_2_Day_20_Brute_Force/Backtracking, Udemy_Backtracking/Recursion, Big_O_Time_O(n\*n!)_Space_O(n+n!) | 319 | 80.00
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| 0045 |[Jump Game II](src/main/dart/g0001_0100/s0045_jump_game_ii)| Medium | Top_100_Liked_Questions, Array, Dynamic_Programming, Greedy, Algorithm_II_Day_13_Dynamic_Programming, Dynamic_Programming_I_Day_4, Big_O_Time_O(n)_Space_O(1) | 335 | 81.58
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| 0042 |[Trapping Rain Water](src/main/dart/g0001_0100/s0042_trapping_rain_water)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Two_Pointers, Stack, Monotonic_Stack, Dynamic_Programming_I_Day_9, Udemy_Two_Pointers, Big_O_Time_O(n)_Space_O(1) | 328 | 80.77
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| 0041 |[First Missing Positive](src/main/dart/g0001_0100/s0041_first_missing_positive)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Udemy_Arrays, Big_O_Time_O(n)_Space_O(n) | 355 | 85.19
1277+
| 0039 |[Combination Sum](src/main/dart/g0001_0100/s0039_combination_sum)| Medium | Top_100_Liked_Questions, Array, Backtracking, Algorithm_II_Day_10_Recursion_Backtracking, Level_2_Day_20_Brute_Force/Backtracking, Udemy_Backtracking/Recursion, Big_O_Time_O(2^n)_Space_O(n+2^n) | 316 | 96.88
12451278
| 0035 |[Search Insert Position](src/main/dart/g0001_0100/s0035_search_insert_position)| Easy | Top_100_Liked_Questions, Array, Binary_Search, Algorithm_I_Day_1_Binary_Search, Binary_Search_I_Day_2, Big_O_Time_O(log_n)_Space_O(1) | 325 | 80.73
12461279
| 0034 |[Find First and Last Position of Element in Sorted Array](src/main/dart/g0001_0100/s0034_find_first_and_last_position_of_element_in_sorted_array)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Binary_Search, Algorithm_II_Day_1_Binary_Search, Binary_Search_I_Day_5, Big_O_Time_O(log_n)_Space_O(1) | 321 | 92.86
12471280
| 0033 |[Search in Rotated Sorted Array](src/main/dart/g0001_0100/s0033_search_in_rotated_sorted_array)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Binary_Search, Algorithm_II_Day_1_Binary_Search, Binary_Search_I_Day_11, Level_2_Day_8_Binary_Search, Udemy_Binary_Search, Big_O_Time_O(log_n)_Space_O(1) | 317 | 91.14

‎src/main/dart/g0001_0100/s0008_string_to_integer_atoi/readme.md

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// check owerflow
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if (sign == -1 && res < (MIN + digit) / 10) {
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return MIN;
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}
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else if (res > (MAX - digit) / 10) {
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} else if (res > (MAX - digit) / 10) {
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return MAX;
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}
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‎src/main/dart/g0001_0100/s0039_combination_sum/readme.md

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[![](https://img.shields.io/github/stars/LeetCode-in-Dart/LeetCode-in-Dart?label=Stars&style=flat-square)](https://github.com/LeetCode-in-Dart/LeetCode-in-Dart)
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[![](https://img.shields.io/github/forks/LeetCode-in-Dart/LeetCode-in-Dart?label=Fork%20me%20on%20GitHub%20&style=flat-square)](https://github.com/LeetCode-in-Dart/LeetCode-in-Dart/fork)
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## 39\. Combination Sum
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Medium
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Given an array of **distinct** integers `candidates` and a target integer `target`, return _a list of all **unique combinations** of_ `candidates` _where the chosen numbers sum to_ `target`_._ You may return the combinations in **any order**.
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The **same** number may be chosen from `candidates` an **unlimited number of times**. Two combinations are unique if the frequency of at least one of the chosen numbers is different.
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It is **guaranteed** that the number of unique combinations that sum up to `target` is less than `150` combinations for the given input.
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**Example 1:**
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**Input:** candidates = [2,3,6,7], target = 7
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**Output:** [[2,2,3],[7]]
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**Explanation:**
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2 and 3 are candidates, and 2 + 2 + 3 = 7. Note that 2 can be used multiple times.
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7 is a candidate, and 7 = 7.
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These are the only two combinations.
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**Example 2:**
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**Input:** candidates = [2,3,5], target = 8
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**Output:** [[2,2,2,2],[2,3,3],[3,5]]
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**Example 3:**
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**Input:** candidates = [2], target = 1
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**Output:** []
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**Constraints:**
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* `1 <= candidates.length <= 30`
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* `1 <= candidates[i] <= 200`
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* All elements of `candidates` are **distinct**.
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* `1 <= target <= 500`
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## Solution
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```dart
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class Solution {
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List<List<int>> combinationSum(List<int> coins, int amount) {
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List<List<int>> ans = [];
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List<int> subList = [];
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combinationSumRec(coins.length, coins, amount, subList, ans);
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return ans;
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}
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void combinationSumRec(int n, List<int> coins, int amount, List<int> subList, List<List<int>> ans) {
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if (amount == 0 || n == 0) {
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if (amount == 0) {
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// Create a new list from subList and add to ans
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ans.add(List.from(subList));
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}
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return;
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}
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if (amount - coins[n - 1] >= 0) {
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subList.add(coins[n - 1]);
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combinationSumRec(n, coins, amount - coins[n - 1], subList, ans);
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// Remove the last element
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subList.removeLast();
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}
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combinationSumRec(n - 1, coins, amount, subList, ans);
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}
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}
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```

‎src/main/dart/g0001_0100/s0041_first_missing_positive/readme.md

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[![](https://img.shields.io/github/stars/LeetCode-in-Dart/LeetCode-in-Dart?label=Stars&style=flat-square)](https://github.com/LeetCode-in-Dart/LeetCode-in-Dart)
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[![](https://img.shields.io/github/forks/LeetCode-in-Dart/LeetCode-in-Dart?label=Fork%20me%20on%20GitHub%20&style=flat-square)](https://github.com/LeetCode-in-Dart/LeetCode-in-Dart/fork)
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## 41\. First Missing Positive
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Hard
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Given an unsorted integer array `nums`, return the smallest missing positive integer.
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You must implement an algorithm that runs in `O(n)` time and uses constant extra space.
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**Example 1:**
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**Input:** nums = [1,2,0]
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**Output:** 3
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**Explanation:** The numbers in the range [1,2] are all in the array.
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**Example 2:**
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**Input:** nums = [3,4,-1,1]
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**Output:** 2
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**Explanation:** 1 is in the array but 2 is missing.
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**Example 3:**
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**Input:** nums = [7,8,9,11,12]
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**Output:** 1
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**Explanation:** The smallest positive integer 1 is missing.
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**Constraints:**
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* <code>1 <= nums.length <= 10<sup>5</sup></code>
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* <code>-2<sup>31</sup> <= nums[i] <= 2<sup>31</sup> - 1</code>
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## Solution
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```dart
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class Solution {
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int firstMissingPositive(List<int> nums) {
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int i = 0, n = nums.length;
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while (i < n) {
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int j = nums[i] - 1;
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if (0 <= j && j < n && nums[i] != nums[j]) {
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// swap
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int tmp = nums[i];
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nums[i] = nums[j];
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nums[j] = tmp;
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} else {
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i++;
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}
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}
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for (int i = 0; i < n; i++) {
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if (nums[i] != i + 1) {
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return i + 1;
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}
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}
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return n + 1;
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}
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}
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```

‎src/main/dart/g0001_0100/s0042_trapping_rain_water/readme.md

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[![](https://img.shields.io/github/stars/LeetCode-in-Dart/LeetCode-in-Dart?label=Stars&style=flat-square)](https://github.com/LeetCode-in-Dart/LeetCode-in-Dart)
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## 42\. Trapping Rain Water
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Hard
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Given `n` non-negative integers representing an elevation map where the width of each bar is `1`, compute how much water it can trap after raining.
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**Example 1:**
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![](https://assets.leetcode.com/uploads/2018/10/22/rainwatertrap.png)
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**Input:** height = [0,1,0,2,1,0,1,3,2,1,2,1]
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**Output:** 6
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**Explanation:** The above elevation map (black section) is represented by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of rain water (blue section) are being trapped.
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**Example 2:**
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**Input:** height = [4,2,0,3,2,5]
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**Output:** 9
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**Constraints:**
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* `n == height.length`
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* <code>1 <= n <= 2 * 10<sup>4</sup></code>
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* <code>0 <= height[i] <= 10<sup>5</sup></code>
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## Solution
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```dart
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import 'dart:math';
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class Solution {
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int trap(List<int> heigth) {
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int left = 0,
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right = heigth.length - 1,
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leftMax = 0,
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rightMax = 0,
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water = 0;
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while (left < right) {
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leftMax = max(leftMax, heigth[left]);
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rightMax = max(rightMax, heigth[right]);
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water += leftMax < rightMax
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? leftMax - heigth[left++]
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: rightMax - heigth[right--];
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}
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return water;
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}
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}
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```

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