[5] 最长回文子串

src/leecode/javascript/5.最长回文子串.js

@@ -0,0 +1,51 @@
+/*
+ * @lc app=leetcode.cn id=5 lang=javascript
+ *
+ * [5] 最长回文子串
+ */
+
+// @lc code=start
+/**
+ * @param {string} s
+ * @return {string}
+ */
+var longestPalindrome = function (s) {
+  const l = s.length;
+  let ret = "";
+  for (let i = 0; i < l; i++) {
+    let sFront = i - 1,
+      sTail = i + 1,
+      dFront = i,
+      dTail = i + 1;
+    let sRet = s.charAt(i),
+      dRet = "";
+    while ((sFront >= 0 && sTail <= l - 1) || (dFront >= 0 && dTail <= l - 1)) {
+      if (sFront >= 0 && sTail <= l - 1) {
+        if (s.charAt(sFront) == s.charAt(sTail)) {
+          sRet = s.charAt(sFront).concat(sRet).concat(s.charAt(sFront));
+          sFront -= 1;
+          sTail += 1;
+        } else {
+          sFront = -1;
+        }
+      }
+      if (dFront >= 0 && dTail <= l - 1) {
+        if (s.charAt(dFront) == s.charAt(dTail)) {
+          dRet = s.charAt(dFront).concat(dRet).concat(s.charAt(dFront));
+          dFront -= 1;
+          dTail += 1;
+        } else {
+          dFront = -1;
+        }
+      }
+    }
+    if (sRet.length > ret.length) {
+      ret = sRet;
+    }
+    if (dRet.length > ret.length) {
+      ret = dRet;
+    }
+  }
+  return ret;
+};
+// @lc code=end