Path Sum II

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]
]

Solution:

/**
* Definition for a binary tree node.
* struct TreeNode {
*     int val;
*     TreeNode *left;
*     TreeNode *right;
*     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector<vector<int>> pathSum(TreeNode* root, int sum) {
vector<vector<int> > res;
vector<int> path;
dfs(root, sum, path, res);

return res;
}

void dfs(TreeNode* root, int sum, vector<int> &path, vector<vector<int> > &res)
{
if(!root) return ;
int val = root->val;
path.push_back(val);
if(!root->left && !root->right)
{
if(val == sum) res.push_back(path);
}
dfs(root->left, sum - val, path, res);
dfs(root->right, sum - val, path, res);
path.pop_back();
}
};