Sum Root to Leaf Numbers

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.

由于加到和里面的值跟其所处节点的层数有关系，所以需要记录这一信息，这里用了一个vector来存，因为顺序代表着以一种层次关系。然后用一个全局的sum来累加。

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
   int sum = 0;
	void sums(TreeNode*root,vector<int>vec)
	{
		if (!root)
			return;
		vec.push_back(root->val);
		if (!root->left && !root->right)
		{
			int count = vec.size()-1;
			for (auto i : vec)
			{
				sum += pow(10.0,count)*i;
				--count;
			}
			return;
		}
		sums(root->left,vec);
		sums(root->right,vec);
	}

	int sumNumbers(TreeNode* root)
	{
		vector<int>vec;
		sums(root,vec);
		return sum;
	}
};