Path Sum II

Problem 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:

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:

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

Example 3:

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

Solution (Go)

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func pathSum(root *TreeNode, targetSum int) [][]int {
	var paths [][]int
	findPaths(root, targetSum, []int{}, &paths)
	return paths
}
func findPaths(node *TreeNode, target int, path []int, paths *[][]int) {
	if node == nil {
		return
	}
	path = append(path, node.Val)
	if node.Val == target && node.Left == nil && node.Right == nil {
		// Create a copy so changes to path variable will not affect res
		tmp := make([]int, len(path))
		copy(tmp, path)
		*paths = append(*paths, tmp)
	}
	findPaths(node.Left, target-node.Val, path, paths)
	findPaths(node.Right, target-node.Val, path, paths)
}