LeetCode [112] Path Sum

112. Path Sum

Easy

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.

Accepted

485,008

Submissions

1,180,295

/**
 * 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;
 *     }
 * }
 */
class Solution {
    public boolean hasPathSum(TreeNode root, int sum) {
        return helper(root, sum, 0);
    }
    
    boolean helper(TreeNode node, int sum, int cur){
        if(node == null) return false;
        cur += node.val;
        if(node.left==null && node.right==null && cur==sum) return true;
        return(helper(node.left, sum, cur) || helper(node.right, sum, cur));
    }
}