codeforces 574B Bear and Three Musketeers

http://codeforces.com/problemset/problem/574/B 题意：给定一个无相图。选出三个点，使得这三个点之间互相有边相连，且三个点的度数之和最小。思路：暴力出奇迹。复杂度o(n2+n*m)

 1/* ***********************************************
 2Author :111qqz
 3Created Time :2015年12月09日 星期三 21时33分28秒
 4File Name :code/cf/problem/574B.cpp
 5************************************************ */
 6
 7#include <cstdio>
 8#include <cstring>
 9#include <iostream>
10#include <algorithm>
11#include <vector>
12#include <queue>
13#include <set>
14#include <map>
15#include <string>
16#include <cmath>
17#include <cstdlib>
18#include <ctime>
19#define fst first
20#define sec second
21#define lson l,m,rt<<1
22#define rson m+1,r,rt<<1|1
23#define ms(a,x) memset(a,x,sizeof(a))
24typedef long long LL;
25#define pi pair < int ,int >
26#define MP make_pair
27
28using namespace std;
29const double eps = 1E-8;
30const int dx4[4]={1,0,0,-1};
31const int dy4[4]={0,-1,1,0};
32const int inf = 0x3f3f3f3f;
33const int N=4E3+7;
34int n ,m;
35vector<int>edge[N];
36int ans;
37
38bool conc[N][N];
39int d[N];
40int main()
41{
42	#ifndef  ONLINE_JUDGE
43	freopen("code/in.txt","r",stdin);
44  #endif
45
46	cin>>n>>m;
47	ms(conc,false);
48	ms(d,0);
49	for ( int i = 0 ; i < m ;i++)
50	{
51	    int x,y;
52	    cin>>x>>y;
53	    conc[x][y] = true;
54	    conc[y][x] = true;
55	    d[x]++;
56	    d[y]++;
57	}
58	int ans = inf;
59	for ( int i = 1 ; i <= n ; i++)
60	    for ( int j = 1 ; j <= n ;j++)
61		if (conc[i][j]&&d[i]+d[j]<ans)
62		{
63		    for ( int k = 1 ; k <= n ; k++)
64			if (conc[i][k]&&conc[j][k])
65			    ans = min(ans,d[i]+d[j]+d[k]);
66		}
67	if (ans!=inf)
68	cout<<ans-6<<endl;
69	else puts("-1");
70
71  #ifndef ONLINE_JUDGE
72  fclose(stdin);
73  #endif
74    return 0;
75}

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