说明：  Description 给出一棵二叉树的结构,判断这棵二叉树是不是完全二叉树。必须使用二叉树类实现。 Input Format 输入文件一共包含N+1行。 第一行含有一个正整数N，代表树中结点总数。 第二行到第N+1行，每行包含二个整数。其中第i行的二个整数Pi，Qi，代表结点i的左孩子为Pi，右孩子为Qi。若Pi=0，则表明结点i没有左孩子。同样的，若Qi=0，则表明结点i没有右孩子。(第i行指的是这N行中的第i行) Output Format 如果给出的树是完全二叉树，则输出 Y ,否则输出 N 。(均不包含引号)
(Description is given a binary tree structure to determine binary tree is not complete binary tree. You must use a binary tree class implementation. Input Format input file contains a total N+1 line. The first line contains a positive integer N, the total number of nodes in the tree representation. N+1 second line to the first line, each line contains two integers. Wherein the i-th row of two integers Pi, Qi, representative of the left child node i is Pi, the right child of Qi. If Pi = 0, it indicates that there is no left child node i. Similarly, if Qi = 0, it indicates that there is no right child node i. (Referring to the i-th row in the first line of this N i lines) Output Format If the tree is a complete binary tree is given, the output ' Y' , otherwise the output ' N' . (Exclude quotes))