题解 | #二叉树根节点到叶子节点的所有路径和#

public int sumNumbers (TreeNode root) {
// write code here
if(root == null){
return 0;
}

    int val = root.val;
    if(root.left != null){
        root.left.val = Integer.valueOf(String.valueOf(val) + root.left.val);
    }

    if(root.right != null){
        root.right.val = Integer.valueOf(String.valueOf(val) + root.right.val);
    }

    if(root.left == null && root.right == null){
        return val;
    }

    return sumNumbers(root.left) + sumNumbers(root.right);
}