sum-root-to-leaf-numbers

sum-root-to-leaf-numbers

题目描述

Given a binary tree containing digits from0-9only, each root-to-leaf path could represent a number.

An example is the root-to-leaf path1->2->3which represents the number123.

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

For example,

    1   / \  2   3

The root-to-leaf path1->2represents the number12.

The root-to-leaf path1->2represents the number12.
The root-to-leaf path1->3represents the number13.

Return the sum = 12 + 13 =25.

思想

主要是树的遍历，dfs

这也考察了递归遍历时的处理

代码

class Solution {public:    int sumNumbers(TreeNode *root) {        if(root == NULL) return 0;        int res = 0, s = 0;        dfs(root, res, s);        return res;    }    void dfs(TreeNode *root, int &res, int s) {        s += root->val;        if(root->left != NULL) {            s = s * 10;            dfs(root->left, res, s);            s = s / 10;        }        if(root->right != NULL) {            s = s * 10;            dfs(root->right, res, s);            s = s / 10;        }        if(root->left == NULL && root->right == NULL) {            res += s;        }        return;    }};