LeetCode题解：Sum Root to Leaf Numbers

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.

题意：给定二叉树，其从根结点到叶子结点的路径代表一个整数，求所有路径的和

解决思路：dfs

代码：

public class Solution {
public int sumNumbers(TreeNode root) {
if(root == null){
return 0;
}

return dfs(root, 0);
}

private int dfs(TreeNode root, int sum){
if(root.left == null && root.right == null){
return sum * 10 + root.val;
}

int result = 0;

if(root.left != null){
result += dfs(root.left, sum * 10 + root.val);
}

if(root.right != null){
result += dfs(root.right, sum * 10 + root.val);
}

return result;
}
}