Path Sum

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

return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23

/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ public class Solution { public boolean hasPathSum(TreeNode root, int sum) { return dfs(root,0,sum); } private boolean dfs(TreeNode root, int curSum,int sum){ if(root==null)return false; curSum+=root.val;//preorder traversal //check if it is leaf if(root.left==null&&root.right==null) return curSum==sum; return (dfs(root.left,curSum,sum)|| dfs(root.right,curSum,sum)); } }