原创文章，拒绝转载
题目来源：https://leetcode.com/problems/path-sum-ii/description/
Given a binary tree and a sum, find all root-to-leaf paths where each path‘s sum equals the given sum.
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]
]
class Solution {
void dfs(vector<vector<int>>& res, vector<int>& path, TreeNode* root, int sum) {
if (root -> left == NULL && root -> right == NULL) {
if (sum == root -> val) {
path.push_back(root -> val);
res.push_back(path);
path.pop_back();
}
return;
}
if (root -> left != NULL) {
path.push_back(root -> val);
dfs(res, path, root -> left, sum - (root -> val));
path.pop_back();
}
if (root -> right != NULL) {
path.push_back(root -> val);
dfs(res, path, root -> right, sum - (root -> val));
path.pop_back();
}
}
public:
vector<vector<int>> pathSum(TreeNode* root, int sum) {
vector<vector<int>> res;
if (root == NULL)
return res;
vector<int> path;
dfs(res, path, root, sum);
return res;
}
};这道题目题意是，在一棵二叉树中，寻找一个从根节点到叶子节点的路径，使得路径上的数字之和为给定的数字sum，要求找出所有这样的路径。当然最容易想到的就是使用DFS来解决。
原文：http://www.cnblogs.com/yanhewu/p/7995213.html