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Jul 4, 2025
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feat: add solutions to lc problem: No.1394 #4547

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90 changes: 49 additions & 41 deletions solution/1300-1399/1394.Find Lucky Integer in an Array/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -81,9 +81,9 @@ tags:

### 方法一：计数

我们可以用哈希表或数组 $cnt$ 统计 $arr$ 中每个数字出现的次数，然后遍历 $cnt$，找到满足 $cnt[x] = x$ 的最大的 $x$ 即可。如果没有这样的 $x$，则返回 $-1$。
我们可以用哈希表或数组 $\textit{cnt}$ 统计 $\textit{arr}$ 中每个数字出现的次数，然后遍历 $\textit{cnt}$，找到满足 $\textit{cnt}[x] = x$ 的最大的 $x$ 即可。如果没有这样的 $x$，则返回 $-1$。

时间复杂度 $O(n)$，空间复杂度 $O(n)$。其中 $n$ 为 $arr$ 的长度。
时间复杂度 $O(n)$，空间复杂度 $O(n)$。其中 $n$ 为 $\textit{arr}$ 的长度。

<!-- tabs:start -->

Expand All @@ -93,29 +93,24 @@ tags:
class Solution:
def findLucky(self, arr: List[int]) -> int:
cnt = Counter(arr)
ans = -1
for x, v in cnt.items():
if x == v and ans < x:
ans = x
return ans
return max((x for x, v in cnt.items() if x == v), default=-1)
```

#### Java

```java
class Solution {
public int findLucky(int[] arr) {
int[] cnt = new int[510];
for (int x : cnt) {
int[] cnt = new int[501];
for (int x : arr) {
++cnt[x];
}
int ans = -1;
for (int x = 1; x < cnt.length; ++x) {
if (cnt[x] == x) {
ans = x;
for (int x = cnt.length - 1; x > 0; --x) {
if (x == cnt[x]) {
return x;
}
}
return ans;
return -1;
}
}
```
Expand All @@ -126,18 +121,16 @@ class Solution {
class Solution {
public:
int findLucky(vector<int>& arr) {
int cnt[510];
memset(cnt, 0, sizeof(cnt));
int cnt[501]{};
for (int x : arr) {
++cnt[x];
}
int ans = -1;
for (int x = 1; x < 510; ++x) {
if (cnt[x] == x) {
ans = x;
for (int x = 500; x; --x) {
if (x == cnt[x]) {
return x;
}
}
return ans;
return -1;
}
};
```
Expand All @@ -146,35 +139,51 @@ public:

```go
func findLucky(arr []int) int {
cnt := [510]int{}
cnt := [501]int{}
for _, x := range arr {
cnt[x]++
}
ans := -1
for x := 1; x < len(cnt); x++ {
if cnt[x] == x {
ans = x
for x := len(cnt) - 1; x > 0; x-- {
if x == cnt[x] {
return x
}
}
return ans
return -1
}
```

#### TypeScript

```ts
function findLucky(arr: number[]): number {
const cnt = Array(510).fill(0);
const cnt: number[] = Array(501).fill(0);
for (const x of arr) {
++cnt[x];
}
let ans = -1;
for (let x = 1; x < cnt.length; ++x) {
if (cnt[x] === x) {
ans = x;
for (let x = cnt.length - 1; x; --x) {
if (x === cnt[x]) {
return x;
}
}
return ans;
return -1;
}
```

#### Rust

```rust
use std::collections::HashMap;

impl Solution {
pub fn find_lucky(arr: Vec<i32>) -> i32 {
let mut cnt = HashMap::new();
arr.iter().for_each(|&x| *cnt.entry(x).or_insert(0) += 1);
cnt.iter()
.filter(|(&x, &v)| x == v)
.map(|(&x, _)| x)
.max()
.unwrap_or(-1)
}
}
```

Expand All @@ -187,17 +196,16 @@ class Solution {
* @return Integer
*/
function findLucky($arr) {
$max = -1;
for ($i = 0; $i < count($arr); $i++) {
$hashtable[$arr[$i]] += 1;
$cnt = array_fill(0, 501, 0);
foreach ($arr as $x) {
$cnt[$x]++;
}
$keys = array_keys($hashtable);
for ($j = 0; $j < count($keys); $j++) {
if ($hashtable[$keys[$j]] == $keys[$j]) {
$max = max($max, $keys[$j]);
for ($x = 500; $x > 0; $x--) {
if ($cnt[$x] === $x) {
return $x;
}
}
return $max;
return -1;
}
}
```
Expand Down
90 changes: 49 additions & 41 deletions solution/1300-1399/1394.Find Lucky Integer in an Array/README_EN.md
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Original file line number Diff line number Diff line change
Expand Up @@ -65,9 +65,9 @@ tags:

### Solution 1: Counting

We can use a hash table or array $cnt$ to count the occurrences of each number in $arr$, then traverse $cnt$ to find the largest $x$ that satisfies $cnt[x] = x$. If there is no such $x$, return $-1$.
We can use a hash table or an array $\textit{cnt}$ to count the occurrences of each number in $\textit{arr}$. Then, we iterate through $\textit{cnt}$ to find the largest $x$ such that $\textit{cnt}[x] = x$. If there is no such $x$, return $-1$.

The time complexity is $O(n)$, and the space complexity is $O(n)$. Where $n$ is the length of $arr$.
The time complexity is $O(n)$, and the space complexity is $O(n)$, where $n$ is the length of the $\textit{arr}$.

<!-- tabs:start -->

Expand All @@ -77,29 +77,24 @@ The time complexity is $O(n)$, and the space complexity is $O(n)$. Where $n$ is
class Solution:
def findLucky(self, arr: List[int]) -> int:
cnt = Counter(arr)
ans = -1
for x, v in cnt.items():
if x == v and ans < x:
ans = x
return ans
return max((x for x, v in cnt.items() if x == v), default=-1)
```

#### Java

```java
class Solution {
public int findLucky(int[] arr) {
int[] cnt = new int[510];
for (int x : cnt) {
int[] cnt = new int[501];
for (int x : arr) {
++cnt[x];
}
int ans = -1;
for (int x = 1; x < cnt.length; ++x) {
if (cnt[x] == x) {
ans = x;
for (int x = cnt.length - 1; x > 0; --x) {
if (x == cnt[x]) {
return x;
}
}
return ans;
return -1;
}
}
```
Expand All @@ -110,18 +105,16 @@ class Solution {
class Solution {
public:
int findLucky(vector<int>& arr) {
int cnt[510];
memset(cnt, 0, sizeof(cnt));
int cnt[501]{};
for (int x : arr) {
++cnt[x];
}
int ans = -1;
for (int x = 1; x < 510; ++x) {
if (cnt[x] == x) {
ans = x;
for (int x = 500; x; --x) {
if (x == cnt[x]) {
return x;
}
}
return ans;
return -1;
}
};
```
Expand All @@ -130,35 +123,51 @@ public:

```go
func findLucky(arr []int) int {
cnt := [510]int{}
cnt := [501]int{}
for _, x := range arr {
cnt[x]++
}
ans := -1
for x := 1; x < len(cnt); x++ {
if cnt[x] == x {
ans = x
for x := len(cnt) - 1; x > 0; x-- {
if x == cnt[x] {
return x
}
}
return ans
return -1
}
```

#### TypeScript

```ts
function findLucky(arr: number[]): number {
const cnt = Array(510).fill(0);
const cnt: number[] = Array(501).fill(0);
for (const x of arr) {
++cnt[x];
}
let ans = -1;
for (let x = 1; x < cnt.length; ++x) {
if (cnt[x] === x) {
ans = x;
for (let x = cnt.length - 1; x; --x) {
if (x === cnt[x]) {
return x;
}
}
return ans;
return -1;
}
```

#### Rust

```rust
use std::collections::HashMap;

impl Solution {
pub fn find_lucky(arr: Vec<i32>) -> i32 {
let mut cnt = HashMap::new();
arr.iter().for_each(|&x| *cnt.entry(x).or_insert(0) += 1);
cnt.iter()
.filter(|(&x, &v)| x == v)
.map(|(&x, _)| x)
.max()
.unwrap_or(-1)
}
}
```

Expand All @@ -171,17 +180,16 @@ class Solution {
* @return Integer
*/
function findLucky($arr) {
$max = -1;
for ($i = 0; $i < count($arr); $i++) {
$hashtable[$arr[$i]] += 1;
$cnt = array_fill(0, 501, 0);
foreach ($arr as $x) {
$cnt[$x]++;
}
$keys = array_keys($hashtable);
for ($j = 0; $j < count($keys); $j++) {
if ($hashtable[$keys[$j]] == $keys[$j]) {
$max = max($max, $keys[$j]);
for ($x = 500; $x > 0; $x--) {
if ($cnt[$x] === $x) {
return $x;
}
}
return $max;
return -1;
}
}
```
Expand Down
12 changes: 5 additions & 7 deletions solution/1300-1399/1394.Find Lucky Integer in an Array/Solution.cpp
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Original file line number Diff line number Diff line change
@@ -1,17 +1,15 @@
class Solution {
public:
int findLucky(vector<int>& arr) {
int cnt[510];
memset(cnt, 0, sizeof(cnt));
int cnt[501]{};
for (int x : arr) {
++cnt[x];
}
int ans = -1;
for (int x = 1; x < 510; ++x) {
if (cnt[x] == x) {
ans = x;
for (int x = 500; x; --x) {
if (x == cnt[x]) {
return x;
}
}
return ans;
return -1;
}
};
11 changes: 5 additions & 6 deletions solution/1300-1399/1394.Find Lucky Integer in an Array/Solution.go
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Original file line number Diff line number Diff line change
@@ -1,13 +1,12 @@
func findLucky(arr []int) int {
cnt := [510]int{}
cnt := [501]int{}
for _, x := range arr {
cnt[x]++
}
ans := -1
for x := 1; x < len(cnt); x++ {
if cnt[x] == x {
ans = x
for x := len(cnt) - 1; x > 0; x-- {
if x == cnt[x] {
return x
}
}
return ans
return -1
}
13 changes: 6 additions & 7 deletions solution/1300-1399/1394.Find Lucky Integer in an Array/Solution.java
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Original file line number Diff line number Diff line change
@@ -1,15 +1,14 @@
class Solution {
public int findLucky(int[] arr) {
int[] cnt = new int[510];
for (int x : cnt) {
int[] cnt = new int[501];
for (int x : arr) {
++cnt[x];
}
int ans = -1;
for (int x = 1; x < cnt.length; ++x) {
if (cnt[x] == x) {
ans = x;
for (int x = cnt.length - 1; x > 0; --x) {
if (x == cnt[x]) {
return x;
}
}
return ans;
return -1;
}
}
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