Floyd求最小環 hdu1599 find the mincost route

裸的最小環。

用Floyd實現非常簡單。

代碼如下：

#include<stdio.h>
#include<string.h>

const int N = 128;
const int INF = 0x3f3f3f3f;

int n, m;
int g[N][N];
int dis[N][N];

int floyd () {
    memset(dis, INF, sizeof(dis));
    int minCircle = INF;
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= n; j++)
            dis[i][j] = g[i][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 && g[j][k] != INF && g[k][i] != INF && dis[i][j] + g[j][k] + g[k][i] < minCircle) {
                    minCircle = dis[i][j] + g[j][k] + g[k][i];
                }
            }
        }
        for(int i = 1; i <= n; i++) {
            for(int j = 1; j <= n; j++) {
                if(i != j && dis[i][j] > dis[i][k] + dis[k][j])
                    dis[i][j] = dis[i][k] + dis[k][j];
            }
        }
    }
    return minCircle;
}

int main () {

    while(~scanf("%d%d", &n, &m)) {
        memset(g, INF, sizeof(g));
        for(int i = 0; i < m; i++) {
            int a, b, c;
            scanf("%d%d%d", &a, &b, &c);
            if(c < g[a][b]) {
                g[a][b] = c;
                g[b][a] = c;
            }
        }
        int ans = floyd();
        if(ans == INF)
            printf("It's impossible.\n");
        else printf("%d\n", ans);
    }
    return 0;
}