【Floyd算法】hdu 2868

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小规模用floyd

#include <list>#include <map>#include <set>#include <queue>#include <string>#include <deque>#include <stack>#include <algorithm>#include <iostream>#include <iomanip>#include <cstdio>#include <cmath>#include <cstdlib>#include <limits.h>#include <time.h>#include <string.h>using namespace std;#define LL long long#define PI acos(-1.0)#define Max INT_MAX#define Min INT_MIN#define eps 1e-8#define FRE freopen("a.txt","r",stdin)#define N 201bool g[N][N];bool gg[N][N];int main(){    int n,m;    while(scanf("%d%d",&n,&m)!=EOF){        int i,j,k;        memset(g,false,sizeof(g));        memset(gg,false,sizeof(gg));        while(m--){            int a,b;            scanf("%d%d",&a,&b);            g[a][b]=true;        }        int res=0;        for(i=1;i<=n;i++)        for(j=1;j<=n;j++)        for(k=1;k<=n;k++)        if(g[j][i] && g[i][k]){            g[j][k]=gg[j][k]=true;     // 注意：1 2 2 3 3 4 4 5这组数据，要连上1-3,1-4,1-5。。。。            //cout<<j<<" "<<k<<endl;        }        for(i=1;i<=n;i++)        for(j=i+1;j<=n;j++)        if(gg[i][j] || gg[j][i])        res++;        printf("%d\n",n*(n-1)/2-res);    }    return 0;}