Added task 594.

Author: javadev

src/main/java/g0501_0600/s0594_longest_harmonious_subsequence/Solution.java

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+package g0501_0600.s0594_longest_harmonious_subsequence;
+
+// #Easy #Array #Hash_Table #Sorting
+
+import java.util.Arrays;
+
+public class Solution {
+ public int findLHS(int[] nums) {
+ Arrays.sort(nums);
+ int max = 0;
+ int lastN = 0;
+ int curN = 1;
+ int cur = nums[0];
+ for (int i = 1; i < nums.length; i++) {
+ if (nums[i] > cur) {
+ if (lastN > 0 && curN > 0 && lastN + curN > max) {
+ max = lastN + curN;
+ }
+ // if diff more than 1, don't count
+ lastN = nums[i] - cur == 1 ? curN : 0;
+ curN = 1;
+ cur = nums[i];
+ } else {
+ curN++;
+ }
+ }
+ if (lastN > 0 && curN > 0 && lastN + curN > max) {
+ max = lastN + curN;
+ }
+ return max;
+ }
+}

src/main/java/g0501_0600/s0594_longest_harmonious_subsequence/readme.md

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+594\. Longest Harmonious Subsequence
+
+Easy
+
+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_.
+
+A **subsequence** of array is a sequence that can be derived from the array by deleting some or no elements without changing the order of the remaining elements.
+
+**Example 1:**
+
+**Input:** nums = [1,3,2,2,5,2,3,7]
+
+**Output:** 5
+
+**Explanation:** The longest harmonious subsequence is [3,2,2,2,3]. 
+
+**Example 2:**
+
+**Input:** nums = [1,2,3,4]
+
+**Output:** 2 
+
+**Example 3:**
+
+**Input:** nums = [1,1,1,1]
+
+**Output:** 0 
+
+**Constraints:**
+
+* <code>1 <= nums.length <= 2 * 10<sup>4</sup></code>
+* <code>-10<sup>9</sup> <= nums[i] <= 10<sup>9</sup></code>

src/test/java/g0501_0600/s0594_longest_harmonious_subsequence/SolutionTest.java

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+package g0501_0600.s0594_longest_harmonious_subsequence;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.MatcherAssert.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class SolutionTest {
+ @Test
+ void findLHS() {
+ assertThat(new Solution().findLHS(new int[] {1, 3, 2, 2, 5, 2, 3, 7}), equalTo(5));
+ }
+
+ @Test
+ void findLHS2() {
+ assertThat(new Solution().findLHS(new int[] {1, 2, 3, 4}), equalTo(2));
+ }
+
+ @Test
+ void findLHS3() {
+ assertThat(new Solution().findLHS(new int[] {1, 1, 1, 1}), equalTo(0));
+ }
+}