Create 3045-count-prefix-and-suffix-pairs-ii.js

Author: everthis

3045-count-prefix-and-suffix-pairs-ii.js

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+class Trie {
+  constructor() {
+    this.word = null
+    this.children = new Array(27)
+    this.cnt = 0
+  }
+}
+/**
+ * @param {string[]} words
+ * @return {number}
+ */
+var countPrefixSuffixPairs = function (words) {
+  const M = 31
+  let rt1 = new Trie()
+  let rt2 = new Trie()
+  let res = 0
+
+  for (let w of words) {
+    res += addAndCount(w)
+  }
+
+  return res
+
+  function addAndCount(w) {
+    let res = 0
+    let pre = rt1
+    let suf = rt2
+    let n = w.length
+
+    for (let i = 0; i < n; i++) {
+      let a = w.charAt(i)
+      let b = w.charAt(n - 1 - i)
+
+      if (!pre.children[a.charCodeAt() & M]) {
+        pre.children[a.charCodeAt() & M] = new Trie()
+      }
+      if (!suf.children[b.charCodeAt() & M]) {
+        suf.children[b.charCodeAt() & M] = new Trie()
+      }
+
+      pre = pre.children[a.charCodeAt() & M]
+      suf = suf.children[b.charCodeAt() & M]
+
+      if (pre.word && suf.word === pre.word) {
+        res += pre.cnt
+      }
+    }
+
+    if (!pre.word) {
+      pre.word = w
+      suf.word = w
+    }
+
+    pre.cnt++
+    suf.cnt++
+
+    return res
+  }
+}