tsanmmmm2000's Tech Blog

Question

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.

For example:
Given the below binary tree and sum = 22,

              5
             / \
            4   8
           /   / \
          11  13  4
         /  \      \
        7    2      1

My C# Solution

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left;
 *     public TreeNode right;
 *     public TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public bool HasPathSum(TreeNode root, int sum) {
        if (root == null) return false;
        
        if (root.left == null && root.right == null) return root.val == sum;
        
        return HasPathSum(root.left, sum - root.val) 
            || HasPathSum(root.right, sum - root.val);
    }
}