113. Path Sum II

Posted on Edited on In

113. Path Sum II

Description

Given the root of a binary tree and an integer targetSum, return all root-to-leaf paths where the sum of the node values in the path equals targetSum. Each path should be returned as a list of the node values , not node references.

A root-to-leaf path is a path starting from the root and ending at any leaf node. A leaf is a node with no children.

Example 1:

1
2
3
4
5
Input: root = [5,4,8,11,null,13,4,7,2,null,null,5,1], targetSum = 22
Output: [[5,4,11,2],[5,8,4,5]]
Explanation: There are two paths whose sum equals targetSum:
5 + 4 + 11 + 2 = 22
5 + 8 + 4 + 5 = 22

Example 2:

1
2
Input: root = [1,2,3], targetSum = 5
Output: []

Example 3:

1
2
Input: root = [1,2], targetSum = 0
Output: []

Constraints:

  • The number of nodes in the tree is in the range [0, 5000].
  • -1000 <= Node.val <= 1000
  • -1000 <= targetSum <= 1000

Hints/Notes

  • N/A

Solution

Language: C++

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
/**
 * 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<int> cur;
    vector<vector<int>> res;
    int curSum = 0;
    int targetSum_;

    vector<vector<int>> pathSum(TreeNode* root, int targetSum) {
        targetSum_ = targetSum;
        traverse(root);
        return res;
    }

    void traverse(TreeNode* root) {
        if (!root) {
            return;
        }

        curSum += root->val;
        cur.push_back(root->val);

        if (!root->left && !root->right && curSum == targetSum_) {
            res.push_back(cur);
        }

        traverse(root->left);
        traverse(root->right);

        cur.pop_back();
        curSum -= root->val;
    }
};