[leetcode] 129. Sum Root to Leaf Numbers : https://leetcode.com/problems/sum-root-to-leaf-numbers/

Sum Root to Leaf Numbers.cc

/**
 * 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 ans = 0;

    void setAns(TreeNode* root, int sum){
        if(root == NULL) return;
        sum += root->val;
        if(root->left == NULL && root->right ==NULL)
            ans += sum;
        sum *= 10;
        setAns(root->left, sum);
        setAns(root->right, sum);
    }
    
    int sumNumbers(TreeNode* root) {
        ans = 0;
        setAns(root, 0);
        return ans;
    }
};