Update 2791-count-paths-that-can-form-a-palindrome-in-a-tree.js

Author: everthis

2791-count-paths-that-can-form-a-palindrome-in-a-tree.js

@@ -1,3 +1,44 @@
+/**
+ * @param {number[]} parent
+ * @param {string} s
+ * @return {number}
+ */
+const countPalindromePaths = function (parent, s) {
+  const n = parent.length
+  const nxt = Array.from({ length: n }, () => Array())
+  const cnt = {0:0}
+  for(let i = 1; i < n; i++) {
+    nxt[parent[i]].push([i, s[i]])
+  }
+  let res = 0
+  dfs(0, -1, 0)
+  return res
+
+  function dfs(node, parent, state) {
+    if(cnt[state] != null) res += cnt[state]
+    for(let i = 0; i < 26; i++) {
+      const tmp = state ^ (1 << i)
+      if(cnt[tmp] != null) res += cnt[tmp]
+    }
+    if(cnt[state] == null) cnt[state] = 0
+    cnt[state] += 1
+
+    for(const [next, ch] of (nxt[node] || [])) {
+      if(next === parent) continue
+      dfs(next, node, state ^ getMask(ch))
+    }
+
+  }
+
+}
+function getMask(c) {
+  const a = 'a'.charCodeAt(0)
+  return 1 << (c.charCodeAt(0) - a)
+}
+
+
+// another
+
 /**
  * @param {number[]} parent
  * @param {string} s