原题链接: https://oj.leetcode.com/problems/path-sum/

public boolean hasPathSum(TreeNode root, int sum) {
    if (root == null) return false;

    if (root.left == null && root.right == null && root.val == sum) {
        return true;
    } if (hasPathSum(root.left, sum - root.val) || hasPathSum(root.right, sum - root.val)) {
        return true;
    }

    return false;
}