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：
本题是112. Path Sum的扩展题，112. Path Sum求个数，本题求具体所有的路径，采用回朔法。
代码如下：
class Solution {
vector<vector<int>> ret;
public:
void pathSumHelper(TreeNode* root, vector<int> & vec, int sum) {
if(root == NULL) return;
vec.push_back(root->val);
if(root->left == NULL && root->right == NULL && sum == root->val)
ret.push_back(vec);
pathSumHelper(root->left, vec, sum-root->val);
pathSumHelper(root->right, vec, sum-root->val);
vec.pop_back();
return;
}
vector<vector<int>> pathSum(TreeNode* root, int sum) {
vector<int> vec;
pathSumHelper(root,vec,sum);
return ret;
}
};
