LeetCode（129） Sum Root to Leaf Numbers

题目

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,

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.

分析

按照二叉树的深度遍历，累计所有路径组成整数的和。

使用二叉树的递归深度优先遍历实现！

AC代码

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    int sumNumbers(TreeNode* root) {        int ret = 0;        if (!root)            return ret;        else if (!root->left && !root->right)        {            ret = root->val;            return ret;        }        else            dfs(root, root->val , ret);        return ret;    }    //深度优先遍历，得到所有根节点到叶子节点的路径和    void dfs(TreeNode *root, int val, int &sum)    {        if (!root->left && !root->right)            sum += val;        if (root->left)        {            dfs(root->left, val * 10 + root->left->val, sum);        }        if (root->right)        {            dfs(root->right, val * 10 + root->right->val, sum);        }    }};

GitHub测试程序源码