LeetCode129 求根到葉子節點數之和

求根都葉子節點數字之和: 遞歸回溯

    public int sumNumbers(TreeNode root){
    //
        return helper(root,0);
    }

    public int helper(TreeNode root,int i){

        if(root==null) return 0;

        int temp = i*10+root.val;
        
        if(root.left==null&&root.right==null){
            return temp;
        }

        return helper(root.left,temp)+helper(root.right,temp);

    }