bzoj1491: [NOI2007]社交网络

题目链接

bzoj1491: [NOI2007]社交网络

题解

n^3枚举一下就没了...

代码

#include<cstdio> 
#include<cstring> 
#include<algorithm> 
 
inline int read() { 
     int x = 0,f = 1 ; 
     char c = getchar(); 
     while(c < '0' || c > '9')c = getchar(); 
     while(c <= '9' && c >= '0') x = x * 10 + c - '0',c = getchar(); 
     return x * f; 
} 
int n,m;
const int maxn = 1007;  
int mp[maxn][maxn]; 
long long cnt[maxn][maxn]; 
double ans[maxn]; 
int main() { 
    n = read(),m = read(); 
    memset(mp,0x3f,sizeof mp); 
    for(int a,b,j = 1;j <= m;++ j) { 
        a = read(),b = read(); 
        mp[a][b] = mp[b][a] = read(); 
        cnt[a][b] = cnt[b][a] = 1; 
    } 
     
    for(int k = 1;k <= n;++ k)  
        for(int i = 1;i <= n;++ i)  
            for(int j = 1;j <= n;++ j) { 
                if(i == k || k == j) continue; 
                if(mp[i][j] > mp[i][k] + mp[k][j]) { 
                    mp[i][j] = mp[i][k] + mp[k][j]; 
                    cnt[i][j] = cnt[i][k] * cnt[k][j]; 
                } 
                else if(mp[i][j] == mp[i][k] + mp[k][j]) 
                    cnt[i][j] += cnt[i][k] * cnt[k][j]; 
            } 
    for(int i = 1;i <= n;++ i) cnt[i][i] = 0 ; 
    for(int x = 1;x <= n;++ x) 
        for(int i = 1;i <= n;++ i) 
            for(int j = 1;j <= n;++ j) 
                if(mp[i][j] == mp[i][x] + mp[x][j] && cnt[i][j]) 
                    ans[x] += (double )cnt[i][x] * cnt[x][j] / (double) cnt[i][j]; 
    for(int i = 1;i <= n;++ i) printf("%.3lf\n",ans[i]); 
    return 0; 
}