Longest Palindromic Substring

Dynamic-Programming/LongestPalindromicSubstring.js

@@ -0,0 +1,47 @@
+/*
+  LeetCode -> https://leetcode.com/problems/longest-palindromic-substring
+
+  Given a string s, find the longest palindromic substring in s.
+  You may assume that the maximum length of s is 1000.
+
+*/
+/**
+ * Finds the longest palindromic substring
+ * @param {string} s Input string 
+ * @returns {string} Longest Palindromic Substring
+ */
+function longestPalindrome(s) {
+    const n = s.length;
+    const dp = new Array(n + 1).fill(0).map(() => new Array(n + 1).fill(0));
+    const len = new Array(n + 1).fill(0).map(() => new Array(n + 1).fill(0));
+    let str = "";
+    let mx = 0;
+//fill for single character
+    for (let i = 0; i < n; i++) {
+        dp[i][i] = 1;
+        len[i][i] = 1;
+    }
+
+    for (let i = n - 2; i >= 0; i--) {
+        for (let j = i + 1; j < n; j++) {
+            if (s[i] === s[j] && j - i === 1) {
+                len[i][j] = 2;
+                dp[i][j] = 1;
+            } else if (s[i] === s[j] && dp[i + 1][j - 1]) {
+                dp[i][j] = 1;
+                len[i][j] = j - i + 1;
+            }
+        }
+    }
+
+    for (let i = 0; i < n; i++) {
+        for (let j = 0; j < n; j++) {
+            if (len[i][j] > mx && dp[i][j]) {
+                mx = len[i][j];
+                str = s.substring(i, j + 1);
+            }
+        }
+    }
+
+    return str;
+}