Merge pull request #449 from suhailmalik07/DP-longest-palindromic-subsequence

Added Longest Palindromic subsequence

Author: pomkarnath98

Dynamic-Programming/LongestPalindromicSubsequence.js

@@ -0,0 +1,39 @@
+/*
+ LeetCode -> https://leetcode.com/problems/longest-palindromic-subsequence/
+
+ Given a string s, find the longest palindromic subsequence's length in s.
+ You may assume that the maximum length of s is 1000.
+
+*/
+
+const longestPalindromeSubsequence = function (s) {
+ const n = s.length
+
+ const dp = new Array(n).fill(0).map(item => new Array(n).fill(0).map(item => 0))
+
+ // fill predefined for single character
+ for (let i = 0; i < n; i++) {
+ dp[i][i] = 1
+ }
+
+ for (let i = 1; i < n; i++) {
+ for (let j = 0; j < n - i; j++) {
+ const col = j + i
+ if (s[j] === s[col]) {
+ dp[j][col] = 2 + dp[j + 1][col - 1]
+ } else {
+ dp[j][col] = Math.max(dp[j][col - 1], dp[j + 1][col])
+ }
+ }
+ }
+
+ return dp[0][n - 1]
+}
+
+const main = () => {
+ console.log(longestPalindromeSubsequence('bbbab')) // 4
+ console.log(longestPalindromeSubsequence('axbya')) // 3
+ console.log(longestPalindromeSubsequence('racexyzcxar')) // 7
+}
+
+main()