BZOJ#1491[NOI2007]社交网络

[NOI2007]社交网络

思路：

使用floyd算法并记录路径，
d[i][j]=d[i][k]*d[k][j]

代码：

#include <bits/stdc++.h>
#define int long long
int _ = 0, Case = 1;
using namespace std;
#define all(v) begin(v),end(v)
#define nline '\n'

const int N = 110;
int g[N][N];
int d[N][N];
double ans[N];
void solve(int Case) {
    int n, m;
    scanf("%lld%lld", &n, &m);
    memset(g, 0x3f, sizeof g);
    for (; m--;) {
        int a, b, w;
        scanf("%lld%lld%lld", &a, &b, &w);
        g[a][b] = g[b][a] = w;
        d[a][b] = d[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 == j or j == k or i == k) continue;
                if (g[i][j] > g[i][k] + g[k][j]) {
                    g[i][j] = g[i][k] + g[k][j];
                    d[i][j] = d[i][k] * d[k][j];
                } else if (g[i][j] == g[i][k] + g[k][j]) {
                    d[i][j] += d[i][k] * d[k][j];
                }
            }
        }
    }
    for (int k = 1; k <= n; k++) {
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= n; j++) {
                if (i == j or j == k or i == k) continue;
                if(g[i][j]==g[i][k]+g[k][j]){
                    ans[k]+=(1.0*d[i][k]*d[k][j])/d[i][j]*1.0;
                }
            }
        }
    }
    for(int i=1;i<=n;i++){
        printf("%.3lf\n",ans[i]);
    }
}

signed main() {
    //ios::sync_with_stdio(false); cin.tie(nullptr);
    //cin >> _; for (Case = 1; Case <= _; Case++)
    solve(Case);

    return 0;
}