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  • PAT 甲级 1110 Complete Binary Tree (25分)

    Given a tree, you are supposed to tell if it is a complete binary tree.

    Input Specification:

    Each input file contains one test case. For each case, the first line gives a positive integer N (≤) which is the total number of nodes in the tree -- and hence the nodes are numbered from 0 to N1. Then N lines follow, each corresponds to a node, and gives the indices of the left and right children of the node. If the child does not exist, a - will be put at the position. Any pair of children are separated by a space.

    Output Specification:

    For each case, print in one line YES and the index of the last node if the tree is a complete binary tree, or NO and the index of the root if not. There must be exactly one space separating the word and the number.

    Sample Input 1:

    9
    7 8
    - -
    - -
    - -
    0 1
    2 3
    4 5
    - -
    - -

    Sample Output 1:

    YES 8

    Sample Input 2:

    8
    - -
    4 5
    0 6
    - -
    2 3
    - 7
    - -
    - -

    Sample Output 2:

    NO 1

    题意:给出 n 个结点,(0-n-1)n 行左右孩子结点,根结点为行中没有出现的结点;

    判断是否为完全二叉树,则输出 (YES)末尾结点则输出(NO)根结点

    AC判断完全二叉树】:1、[ 找出根结点 ]    2、[ DFS遍历 ]   3、[ 分类输出 ]

     1 #include<bits/stdc++.h>
     2 using namespace std;
     3 
     4 struct node{
     5     string left, right;
     6 } Node[21];
     7 
     8 int root= 0, maxn = -1, last;
     9 
    10 void DFS(int root, int index)
    11 {
    12     if(index > maxn)
    13     {
    14         maxn = index;
    15         last = root;
    16     }
    17     if(Node[root].left != "-") DFS(stoi(Node[root].left), index * 2);
    18     if(Node[root].right != "-") DFS(stoi(Node[root].right), index * 2 + 1);
    19 }
    20 
    21 int main()
    22 {
    23     int n; cin >> n;
    24     vector<int> find_root(n, 0);
    25     for(int i = 0; i < n; i++)
    26     {
    27         cin >> Node[i].left >> Node[i].right;
    28         if(Node[i].left != "-") find_root[stoi(Node[i].left)] = 1;
    29         if(Node[i].right != "-") find_root[stoi(Node[i].right)] = 1;
    30     }
    31     
    32     while(root < n && find_root[root]) root++;
    33     DFS(root, 1);
    34     
    35     if(n == maxn) cout << "YES " << last;
    36     else cout << "NO " << root;
    37     return 0;
    38 }
    View Code

    Tips:vector<int> v(n, 0);  // 初始化

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  • 原文地址:https://www.cnblogs.com/kamisamalz/p/13605135.html
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