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.
每到达一个根节点，就代表一个路径访问完成，将和加入总和。
树结构用递归是最容易的，每递归一层，上层的部分和需要乘以10在做加法。
/** * Definition for binary tree * 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 Sum = 0; Helper(root, 0, Sum); return Sum; } void Helper(TreeNode* root, int partSum, int& Sum) { if(root == NULL) return; else if(root->left == NULL && root->right == NULL) //add this path Sum += (10*partSum+root->val); else { Helper(root->left, 10*partSum+root->val, Sum); Helper(root->right, 10*partSum+root->val, Sum); } } };
【LeetCode】Sum Root to Leaf Numbers
原文：http://www.cnblogs.com/ganganloveu/p/4122506.html