path-sum.java

/**
 * 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) {
        if(root == null){
            // exception
            return false;
        }
        if(root.left == null && root.right == null){
            if(sum == root.val){
                return true;
            }
            return false;
        }
        else{
            boolean left = false;
            boolean right = false;
            if(root.left != null){
                left = hasPathSum(root.left, sum-root.val);
            }
            if(root.right != null){
                right = hasPathSum(root.right, sum-root.val);
            }
            return left||right;
        }
    }
}