Path Sum II

最新推荐文章于 2024-10-26 02:26:14 发布

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最新推荐文章于 2024-10-26 02:26:14 发布

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分类专栏： LeetCode 文章标签： LeetCode Path Sum II C++

本文链接：https://blog.youkuaiyun.com/lyh642784803/article/details/52048412

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题目描述：

Given a binary tree and a sum, find all root-to-leaf paths where each path's sum equals the given sum.

For example:
Given the below binary tree and sum = 22 ,

              5
             / \
            4   8
           /   / \
          11  13  4
         /  \    / \
        7    2  5   1

return

[
   [5,4,11,2],
   [5,8,4,5]
]

解题思路：

使用二叉树的先序遍历，如果遍历到叶子结点，就判断路径上结点的和是否等于sum。

AC代码如下：

class Solution {
public:
	vector<vector<int>> pathSum(TreeNode* root, int sum) {
		vector<vector<int>> ans;
		if (root == NULL) return ans;
		vector<int> path;
		help(root, sum, path, ans);
		return ans;
	}

	void help(TreeNode* root, int sum, vector<int>& path,vector<vector<int>>& ans)
	{
		if (root == NULL) return;
		path.push_back(root->val);
		bool isLeaf = (root->left == NULL && root->right == NULL);
		if (isLeaf){
			if (sum == root->val){
				ans.push_back(path);
			}
		}
		else{
			help(root->left, sum - root->val, path, ans);
			help(root->right, sum - root->val, path, ans);
		}
		path.pop_back();
	}
};