Binary Tree Root to Leaf Path Sum Check LeetCode

Problem: Given the root of a binary tree and an integer targetSum, return true if the tree has a root-to-leaf path such that adding up all the values along the path equals targetSum.

A leaf is a node with no children.

 Example 1:

Input: root = [5,4,8,11,null,13,4,7,2,null,null,null,1], targetSum = 22
Output: true
Explanation: The root-to-leaf path with the target sum is shown.

Example 2:

Input: root = [1,2,3], targetSum = 5
Output: false
Explanation: There two root-to-leaf paths in the tree:
(1 --> 2): The sum is 3.
(1 --> 3): The sum is 4.
There is no root-to-leaf path with sum = 5.

Example 3:

Input: root = [], targetSum = 0
Output: false
Explanation: Since the tree is empty, there are no root-to-leaf paths.

 Constraints:

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

This problem is popular in LeetCode and GeeksForGeeks A collection of hundreds of interview questions and solutions are available in our blog at Interview Question

Solution:

	/**
	Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.
	Note: A leaf is a node with no children.
	Example:
	Given the below binary tree and sum = 22,
	5
	/ \
	4 8
	/ / \
	11 13 4
	/ \ \
	7 2 1
	return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.
	*/
	public class BinaryTreeRootToLeafPathSum{
	public boolean hasPathSum(TreeNode root, int sum){
	if(root==null){
	return sum==0;
	}
	//now recursively traverse the tree using DFS and check if the sum is obtained on the DFS path
	int cursum = 0;
	return performDFSTraversal(root, cursum, sum);
	}
	public boolean performDFSTraversal(TreeNode root, int cursum, int sum){
	if(root!=null && root.left==null && root.right==null && root.val+cursum==sum){
	return true;
	}
	if(root.left!=null){
	boolean leftvalid = performDFSTraversal(root.left, cursum+root.val, sum);
	if(leftvalid){
	return true;
	}
	}
	//now check the right branch
	if(root.right!=null){
	return performDFSTraversal(root.right, cursum+root.val, sum);
	}
	return false;
	}
	}

view raw BinaryTreeRootToLeafPathSum.java hosted with ❤ by GitHub