Tree DFS

pathSum.cpp

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