Create 1392-longest-happy-prefix.js

Author: everthis

1392-longest-happy-prefix.js

@@ -0,0 +1,29 @@
+/**
+ * @param {string} s
+ * @return {string}
+ */
+const longestPrefix = function(s) {
+  return s.slice(0, dfa().pop())
+  function dfa() {
+    let i = 1
+    let j = 0
+    const len = s.length
+    const prefix = Array(len + 1).fill(0)
+    while(i < len) {
+      if(s[j] === s[i]) {
+        j++
+        i++
+        prefix[i] = j
+      } else {
+        if(j > 0) j = prefix[j]
+        else {
+          i++
+          prefix[i] = 0
+        }
+      }
+    }
+    return prefix
+  }  
+};
+
+