sum root to leafs nums

最新推荐文章于 2017-04-12 21:58:51 发布

SUN_DRAGON

最新推荐文章于 2017-04-12 21:58:51 发布

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分类专栏：算法

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本文介绍了一种算法，用于计算二叉树中所有从根节点到叶子节点的路径所代表数字的总和。通过深度优先搜索遍历二叉树，并使用向量记录路径上的数字，最终将这些数字转换为整数并求和。

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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.

/**
 * 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;
	vector<int> tempNum;
	int toInt(vector<int>& num)
	{
        if(num.size() == 0)
            return 0;
		int ret = 0;
		for(int i = 0; i < num.size(); i ++)
			ret = ret * 10 + num[i];
		return ret;
	}
	void dfs(TreeNode* root)
	{
		if(root == NULL){
            return;
		}
        tempNum.push_back(root->val);
        if(root->left == NULL && root->right == NULL)
        {
            sum += toInt(tempNum);
        }
		dfs(root->left);
		dfs(root->right);
		tempNum.pop_back();
	}
	int sumNumbers(TreeNode *root) {
		// Start typing your C/C++ solution below
		// DO NOT write int main() function
		sum = 0;
        tempNum.clear();
		dfs(root);
		return sum;
	}
};

只有叶子节点才可加，要判定是否为叶子节点