2023-03-14.md

题目

129. Sum Root to Leaf Numbers

You are given the root of a binary tree containing digits from 0 to 9 only.

Each root-to-leaf path in the tree represents a number.

• For example, the root-to-leaf path 1 -> 2 -> 3 represents the number 123.

Return the total sum of all root-to-leaf numbers. Test cases are generated so that the answer will fit in a 32-bit integer.

A leaf node is a node with no children.

思路

代码

// runtime 82.68% memory 22.31%
var sumNumbers = function(root) {
  let sum = 0
  function dfs(node) {
    if (node == null) return 0
    let count = 0
    count += dfs(node.left)
    count += dfs(node.right)
    count = Math.max(count, 1)
    sum += count * node.val
    return count * 10
  }
  dfs(root)
  return sum
}