feat: Solve longest harmonius subsequence

      - Leetcode, #594

Author: brianr482

longest-harmonius-subsequence.js

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+/**
+ * Leetcode, #594
+ * 
+ * We define a harmounious array as an array where the difference between its
+ * maximum value and its minimum value is exactly 1.
+ * 
+ * Now, given an integer array, you need to find the length of its longest
+ * harmonious subsequence among all its possible subsequences.
+ * 
+ * Constraints:
+ * 1. The length of the input array will not exceed 20,000.
+ */
+
+ /**
+ * @param {number[]} nums
+ * @return {number}
+ */
+function findLHS(nums) {
+  let longest = 0;
+  if (nums.length > 1) {
+    const map = new Map();
+    nums.forEach(number => {
+      const cValue = map.has(number) ? map.get(number) + 1 : 1;
+      map.set(number, cValue);
+      if (map.has(number + 1)) {
+        longest = Math.max(longest, cValue + map.get(number + 1));    
+      }
+      if (map.has(number - 1)) {
+        longest = Math.max(longest, cValue + map.get(number - 1));    
+      }
+    });
+  }
+  return longest;
+};