D. J.:

- Added the leetcode problem and solution for 594

Author: nobodyPerfecZ

README.md

@@ -238,6 +238,7 @@
 - [516 Longest Palindromic Subsequence](https://leetcode.com/problems/longest-palindromic-subsequence/description/)
 - [518 Coin Change II](https://leetcode.com/problems/coin-change-ii/description/)
 - [530 Minimum Absolute Difference in BST](https://leetcode.com/problems/minimum-absolute-difference-in-bst/description/)
+- [594 Longest Harmonious Subsequence](https://leetcode.com/problems/longest-harmonious-subsequence/description/)
 - [637 Average of Levels in Binary Tree](https://leetcode.com/problems/average-of-levels-in-binary-tree/description/)
 - [643 Maximum Average Subarray I](https://leetcode.com/problems/maximum-average-subarray-i/description/)
 - [646 Maximum Length of Pair Chain](https://leetcode.com/problems/maximum-length-of-pair-chain/description/)

awesome_python_leetcode/_594_longest_harmonious_subsequence.py

@@ -0,0 +1,21 @@
+import collections
+from typing import List
+
+
+class Solution:
+    """Base class for all LeetCode Problems."""
+
+    def findLHS(self, nums: List[int]) -> int:
+        """
+        We define a harmonious array as an array where the difference between its
+        maximum value and its minimum value is exactly 1.
+
+        Given an integer array nums, return the length of its longest harmonious
+        subsequence among all its possible subsequences.
+        """
+        lhs = 0
+        count = collections.Counter(nums)
+        for val, freq in count.items():
+            hs = 0 if val - 1 not in count else freq + count[val - 1]
+            lhs = max(lhs, hs)
+        return lhs

tests/test_594_longest_harmonious_subsequence.py

@@ -0,0 +1,19 @@
+from typing import List
+
+import pytest
+
+from awesome_python_leetcode._594_longest_harmonious_subsequence import Solution
+
+
+@pytest.mark.parametrize(
+    argnames=["nums", "expected"],
+    argvalues=[
+        ([1, 3, 2, 2, 5, 2, 3, 7], 5),
+        ([1, 2, 3, 4], 2),
+        ([1, 1, 1, 1], 0),
+    ],
+)
+def test_func(nums: List[int], expected: int):
+    """Tests the solution of a LeetCode problem."""
+    lhs = Solution().findLHS(nums)
+    assert lhs == expected