leetcode[129] Sum Root to Leaf Numbers

给定一个数，从根节点到叶节点是一个值，返回所有的值的和。例如：

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.

思路：DFS + 转换构造为数字

注意，如果引用tmp，那么每次调用完左边或者右边的时候，要pop掉相应边。

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    void dfs129(vector<vector<int> > &path, vector<int> &tmp, TreeNode *root)
    {
        tmp.push_back(root -> val);
        if (!root) return ;
        if (!root -> left && !root -> right)
        {
            path.push_back(tmp);
            return;
        }
        if (root -> left)
        {
            dfs129(path, tmp, root -> left);
            tmp.pop_back();
        }
        if (root -> right)
        {
            dfs129(path, tmp, root -> right);
            tmp.pop_back();
        }
    }
    int decode129(vector<vector<int> > &path)
    {
        int ans = 0, subans = 0;
        for (int i = 0; i < path.size(); i++)
        {
            subans = 0;
            for (int j = 0; j < path[i].size(); j++)
            {
                subans = 10 * subans + path[i][j];
            }
            ans += subans;
        }
        return ans;
    }
    int sumNumbers(TreeNode *root) {
        if (!root) return 0;
        vector<vector<int> > path; 
        vector<int> tmp;
        dfs129(path, tmp, root);
        return decode129(path);
    }
};