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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);    }};

 

leetcode[129] Sum Root to Leaf Numbers