LeetCode——Sum Root to Leaf Numbers

標籤：leetcode

Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number.

An example is the root-to-leaf path 1->2->3 which represents the number 123.

Find the total sum of all root-to-leaf numbers.

For example,

    1   /   2   3

The root-to-leaf path 1->2 represents the number 12.
The root-to-leaf path 1->3 represents the number 13.

Return the sum = 12 + 13 = 25.

給定一個僅包含0-9數位二叉樹，每個根到葉的路徑可以代表一個數。

一個例子 根到葉的路徑 1->2->3 代表數123.

找出所有根到葉 數的和。

想到就是深度優先遍曆。

public int sumNumbers(TreeNode root) {return dfs(root, 0);}public int dfs(TreeNode root, int sum) {if (root == null)return 0;sum = sum * 10 + root.val;if (root.left == null && root.right == null)return sum;return dfs(root.left, sum) + dfs(root.right, sum);}// Definition for binary treepublic class TreeNode {int val;TreeNode left;TreeNode right;TreeNode(int x) {val = x;}}