uva 125

来源：互联网发布：nginx 修改路径编辑：程序博客网时间：2024/04/28 12:51

floyd 算法如果存在无数条路则存在a->a的路 a->b的路径数等于 a->i 和 i->b(0=<i<=_max) 路径数的乘积和

#include<cstdio>#include<cstring>#include<algorithm>using namespace std;const int maxn = 30+5;int n, g[maxn][maxn],ca;int main(){    ca = 0;    while (scanf("%d", &n) == 1)    {        int _max = 0;        memset(g, 0, sizeof(g));        for (int i = 0; i < n; i++)        {            int x, y;            scanf("%d%d", &x, &y);            g[x][y] = 1;            _max = max(_max, max(x, y));        }        for (int k = 0; k <= _max; k++)            for (int i = 0; i <= _max; i++)                for (int j = 0; j <= _max; j++)                    g[i][j] += g[i][k]*g[k][j];        for (int k = 0; k <= _max; k++)            if (g[k][k])                for (int i = 0; i <= _max; i++)                    for (int j = 0; j <= _max; j++)                        if (g[i][k] && g[k][j])                            g[i][j] = -1;        printf("matrix for city %d\n", ca++);        for (int i = 0; i <= _max; i++)        {            for (int j = 0; j <= _max; j++)            {                if (j) putchar(' ');                printf("%d", g[i][j]);            }            puts("");        }    }    return 0;}