feat: longest-palindromic-substring

Author: gwbaik9717

longest-palindromic-substring/gwbaik9717.js

@@ -0,0 +1,51 @@
+// Time complexity: O(n^2)
+// Space complexity: O(n^2)
+
+/**
+ * @param {string} s
+ * @return {string}
+ */
+var longestPalindrome = function (s) {
+  const dp = Array.from({ length: s.length }, () =>
+    Array.from({ length: s.length }, () => false)
+  );
+
+  let answer = "";
+  let start = 0;
+  let end = 0;
+
+  const update = (i, j) => {
+    const newLen = Math.abs(i - j) + 1;
+
+    if (newLen > end - start + 1) {
+      start = i;
+      end = j;
+    }
+  };
+
+  for (let i = s.length - 1; i >= 0; i--) {
+    for (let j = i; j < s.length; j++) {
+      if (i === j) {
+        dp[i][j] = true;
+        update(i, j);
+        continue;
+      }
+
+      if (i + 1 === j) {
+        if (s[i] === s[j]) {
+          dp[i][j] = true;
+          update(i, j);
+        }
+
+        continue;
+      }
+
+      if (dp[i + 1][j - 1] && s[i] === s[j]) {
+        dp[i][j] = true;
+        update(i, j);
+      }
+    }
+  }
+
+  return s.slice(start, end + 1);
+};