Create Manacher.js

Author: everthis

src/Manacher.js

@@ -0,0 +1,31 @@
+// https://segmentfault.com/a/1190000003914228
+function manacher(s) {
+    // Preprocess
+    s = '#' + s.split('').join('#') + '#';
+
+    let RL = new Array(s.length).fill(0);
+    let MaxRight = 0;
+    let pos = 0;
+    let MaxLen = 0;
+
+    for (let i = 0; i < s.length; i++) {
+        if (i < MaxRight) {
+            RL[i] = Math.min(RL[2 * pos - i], MaxRight - i);
+        } else {
+            RL[i] = 1;
+        }
+        // Try to expand, taking care of boundaries
+        while (i - RL[i] >= 0 && i + RL[i] < s.length && s[i - RL[i]] === s[i + RL[i]]) {
+            RL[i]++;
+        }
+        // Update MaxRight and pos
+        if (RL[i] + i - 1 > MaxRight) {
+            MaxRight = RL[i] + i - 1;
+            pos = i;
+        }
+        // Update the length of the longest palindromic substring
+        MaxLen = Math.max(MaxLen, RL[i]);
+    }
+    return MaxLen - 1;
+}
+