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题意

给出一个无向图, n个顶点(顶点id从1开始), m条边.

Hamiltonian cycle: a simple cycle that contains every vertex in a graph.

思路

判断Hamiltonian cycle:

• 该顶点集一定包含n+1个顶点
• 首尾一定相等
• 连通性检查

Sample Input:

6 106 23 41 52 53 14 11 66 31 24 567 5 1 4 3 6 2 56 5 1 4 3 6 29 6 2 1 6 3 4 5 2 64 1 2 5 17 6 1 3 4 5 2 67 6 1 2 5 4 3 1

Sample Output:

YESNONONOYESNO

#include "bits/stdc++.h"using namespace std;const int N = 210;int G[N][N];int main(){//     freopen("input.txt","r",stdin);    int n, m; cin >> n >> m;    for (int i = 0; i < m; ++i) {        int a, b; scanf("%d%d",&a,&b);        G[a][b] = G[b][a] = 1;    }    int k;  cin >> k;    for (int i = 0; i < k; ++i) {        int num;  scanf("%d",&num);        if (num != n+1) {            printf("NO\n");            string s; getline(cin,s);            continue;        }        vector
   
     a(num);        set
    
      cnt;        for (int j = 0; j < num; ++j)  scanf("%d",&a[j]),cnt.insert(a[j]);        if (a.back() != a.front() || cnt.size() != n) {            printf("NO\n");            continue;        }        bool ok = true;        for (int j = 1; j < num; ++j) {            if (!G[a[j]][a[j-1]]) {                ok = false;                break;            }        }        if (ok) printf("YES\n");        else printf("NO\n");    }}
    
   

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