112. Path Sum

Description

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.

Constraints

Approach

Examples

Input:

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

sum=22

Output: true

Explanation:

Solutions

// Definition for a binary tree node.
public class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;
    
    TreeNode() {}
    
    TreeNode(int val) { this.val = val; }
    
    TreeNode(int val, TreeNode left, TreeNode right) {
        this.val = val;
        this.left = left;
        this.right = right;
    }
}

/**
 * Time complexity : 
 * Space complexity : 
 */

class Solution {
    public boolean hasPathSum(TreeNode root, int sum) {
        if(root == null) return false;
        
        sum -= root.val;
        if(root.left == null && root.right == null) {
            return sum == 0;
        }
        
        return hasPathSum(root.left, sum) || 
                hasPathSum(root.right, sum);
    }
}