Longest Palindromic Substring (ignacio-chiazzo#24)

Author: ignacio-chiazzo

LeetcodeProblems/Longest_Palindromic_Substring.js

@@ -0,0 +1,79 @@
+/* 
+https://leetcode.com/problems/longest-palindromic-substring/description/
+
+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.
+
+Example 1:
+
+Input: "babad"
+Output: "bab"
+Note: "aba" is also a valid answer.
+Example 2:
+
+Input: "cbbd"
+Output: "bb"
+*/
+
+
+/**
+ * @param {string} s
+ * @return {string}
+ */
+var longestPalindrome = function(str) {
+	if(str.length == 0)
+		return "";
+	
+    var maxPal = 1; 
+	var posPalStart = 0;
+    var currentPalStart = 0;
+
+	for(var i = 1; i < str.length; i++) {
+        if(str.charAt(i - 1) == str.charAt(i)) { 
+            currentPalStart = i - 1;
+            var currentPal = 2; 
+            var iter = 1;
+            while(i - iter - 1  >= 0 && i + iter < str.length && 
+                str.charAt(i - iter - 1) == str.charAt(i + iter)) {
+                currentPalStart = i - iter - 1;
+                iter++;
+                currentPal += 2;
+            }
+        } 
+        if(currentPal > maxPal) {
+            maxPal = currentPal;
+            posPalStart = currentPalStart;
+        }
+    }
+    
+    for(var i = 1; i < str.length - 1; i++) {
+        if(str.charAt(i - 1) == str.charAt(i + 1)) {
+			currentPal = 1;
+			var iter = 1;
+            while(i - iter >= 0 && i + iter < str.length && 
+                str.charAt(i - iter) == str.charAt(i + iter)) {
+                currentPalStart = i - iter;
+                iter++;
+                currentPal += 2;
+            }
+        }
+        if(currentPal > maxPal) {
+            maxPal = currentPal;
+            posPalStart = currentPalStart;
+        }
+    }
+    
+    return str.slice(posPalStart, posPalStart + maxPal);
+}
+
+var main = function() {
+  console.log(longestPalindrome("pabcdcbte"));
+  console.log(longestPalindrome("bb"));
+  console.log(longestPalindrome(""));
+  console.log(longestPalindrome("bbb"));
+  console.log(longestPalindrome("bbbb"));
+  console.log(longestPalindrome("ptabbbbat"));
+}
+
+module.exports.main = main