---
tags: leetcode
---

# [113. Path Sum II](https://leetcode.com/problems/path-sum-ii/)
---
# My Solution
## The Key Idea for Solving This Coding Question
## C++ Code

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */

class Solution {
public:
    vector<vector<int>> pathSum(TreeNode *root, int targetSum) {
        vector<int> path;

        dfs(root, path, targetSum);
        return answer;
    }

private:
    vector<vector<int>> answer;

    void dfs(TreeNode *root, vector<int> &path, int targetSum) {
        if (root == nullptr) {
            return;
        }

        path.push_back(root->val);
        if (root->left == nullptr && root->right == nullptr &&
            root->val == targetSum) {
            answer.push_back(path);
        }

        dfs(root->left, path, targetSum - root->val);
        dfs(root->right, path, targetSum - root->val);
        path.pop_back();
    }
};

## Time Complexity
$O(n)$
$n$ is the number of nodes in the binary tree referred by `root`.
## Space Complexity
$O(H)$
$H$ is the height of the binary tree referred by `root`.
# Miscellane
<!--
# Test Cases

[5,4,8,11,null,13,4,7,2,null,null,5,1]
22

[1,2,3]
5

[1,2]
0

[5,4,8,11,null,13,4,7,2,null,null,null,1]
22

[1,2]
1

[-2,6,null,0,-6]
4

-->