LeetCode101|路径总和

示例: 
给定如下二叉树，以及目标和 sum = 22，

              5
             / 
            4   8
           /   / 
          11  13  4
         /        
        7    2      1
返回 true, 因为存在目标和为 22 的根节点到叶子节点的路径 5->4->11->2。

public class HashPathSumTest {
    public static void main(String[] args) {
        TreeNode t1 = new TreeNode(5);
        TreeNode t2 = new TreeNode(4);
        TreeNode t3 = new TreeNode(8);
        TreeNode t4 = new TreeNode(11);
        TreeNode t5 = new TreeNode(13);
        TreeNode t6 = new TreeNode(4);
        TreeNode t7 = new TreeNode(7);
        TreeNode t8 = new TreeNode(2);
        TreeNode t9 = new TreeNode(1);
        t1.left = t2;
        t1.right = t3;
        t2.left = t4;
        t3.left = t5;
        t3.right = t6;
        t4.left = t7;
        t4.right = t8;
        t6.right = t9;
        int sum = 22;
        boolean hashPathSum = hashPathSum(t1, sum);
        System.out.println("hashPathSum = " + hashPathSum);


    }

    public static boolean hashPathSum(TreeNode root, int sum) {
        if (root == null) {
            return false;
        }
        if (root.val == sum && root.left == null && root.right == null) {
            return true;
        }
        return hashPathSum(root.left, sum - root.val) || hashPathSum(root.right, sum - root.val);
    }
}