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.
Solution: 1. Recursion (add to sum when reaching the leaf).
2.
Iterative solution.
1 /** 2 * Definition for binary tree 3 * struct TreeNode { 4 * int val; 5 * TreeNode *left; 6 * TreeNode *right; 7 * TreeNode(int x) : val(x), left(NULL), right(NULL) {} 8 * }; 9 */ 10 class Solution { 11 public: 12 int sumNumbers(TreeNode *root) { 13 int sum = 0; 14 sumNumberRe(root, 0, sum); 15 return sum; 16 } 17 18 void sumNumberRe(TreeNode* root, int num, int &sum) 19 { 20 if(!root) return; 21 num = num * 10 + root->val; 22 if(!root->left && !root->right) { 23 sum += num; 24 } 25 sumNumberRe(root->left, num, sum); 26 sumNumberRe(root->right, num, sum); 27 } 28 };
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原文：http://www.cnblogs.com/zhengjiankang/p/3661760.html