leetCode(36):Sum Root to Leaf Numbers 分类： leetCode 2015-07-13 16:00 157人阅读 评论(0) 收藏

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.

/**
 * 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:
    void sumNumber(TreeNode* root, int sum,int& result) 
    {
    	if (root == NULL) return;//直接返回
    
    	sum = sum * 10 + root->val;
    
    	if (root->left == NULL && root->right == NULL) 
    	{//相加求和返回
    		result += sum;
    		return;
    	}
    
    	sumNumber(root->left, sum,result);
    	sumNumber(root->right, sum,result);
    }

    int sumNumbers(TreeNode* root) {
        int result = 0;
	sumNumber(root, 0, result);
    	return result;
    }
};