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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
.
Analyse: DFS. Compute the left and right subtree of the root respectively and add them.
Runtime: 4ms.
1 /** 2 * Definition for a binary tree node. 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 return dfs(root, 0); 14 } 15 int dfs(TreeNode* root, int sum){ 16 if(!root) return 0; 17 if(!root->left && !root->right) return sum * 10 + root->val; 18 19 return dfs(root->left, sum * 10 + root->val) + 20 dfs(root->right, sum * 10 + root->val); 21 } 22 };
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原文地址:http://www.cnblogs.com/amazingzoe/p/4696799.html