129_sumRoottoLeafNumbers

/*
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:
    int sumNumbers(TreeNode* root) {
        int sum=0;
        sumNodes(root,0,sum);
        return sum;
    }
    void sumNodes(TreeNode* root,int tmp,int &sum){
        if(!root) return;
        tmp=tmp*10+root->val;
        if(!root->left && !root->right){
            sum+=tmp;
        } 
        sumNodes(root->left,tmp,sum);
        sumNodes(root->right,tmp,sum);
    }
};