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);
}
};