125 - Numbering Paths

来源：互联网发布：easybcd引导ubuntu灰色编辑：程序博客网时间：2024/05/17 08:11

统计路径数量用warshall算法就行即 a[i][j] += a[i][k]*a[k][j];

但是要判断环的存在 a[k][k] !=0 代表有环只要经过K点则路径数就不确定设为-1；

#include<cstdio>

#include<cstring>

int a[100][100];

int main()
{
    int count = 0,n,x,y;
    while(scanf("%d",&n)==1)
    {
        memset(a,0,sizeof(a));
        int min=-1;
        for(int i = 0; i < n; i++)
        {
            scanf("%d %d",&x,&y);
            a[x][y] = 1;
            if(min < x) min = x;
            if(min < y) min = y;

        }
        for(int k = 0; k <= min; k ++)
            for(int i = 0; i <= min; i++)
                for(int j = 0; j <= min; j++)
                    a[i][j] += a[i][k]*a[k][j];
         for(int k = 0; k <= min; k ++)
         if(a[k][k])
            for(int i = 0; i <= min; i++)
                for(int j = 0; j <= min; j++)
                if(a[i][k]&&a[k][j])
                a[i][j] = -1;
        printf("matrix for city %d\n",count++);
        for(int i = 0; i <= min; i++)
        {
            for(int j = 0; j <= min-1; j++)
                printf("%d ",a[i][j]);
            printf("%d\n",a[i][min]);
        }
    }
    return 0;
}