acm floyd 最短路径

#include <stdio.h>
#include <queue>
#include <iostream>
using namespace std;
#define INF 0xfffff					//因为为了辨别是否有负权，所以INF不能开太大
#define MAX 1100
int  path[MAX][MAX];
bool visit[MAX][MAX];
int result;
int floyd (int n)															//边较为少而稀疏，能一次性求出所有的顶点到顶点的最短路径
{  
    int i, j, k;  
    for (k = 1; k <= n; k++)  
        for (i = 1; i <= n; i++)  
            for (j = 1; j <= n; j++)  
			{
				if(i!=j && j!=k && k!=i)
				{
					if (path[i][k] + path[k][j] < path[i][j])  
					   {
						   return 0;
					   }
					else if(path[i][k] + path[k][j] == path[i][j] && !visit[i][j])
					{
						result--;
						visit[i][j] = true;
					}
				}
			}
}  
void input(int line)
{
	int a, b, weight;
	
	for(int i=1; i<=line; i++)
	{
		for(int j=1; j<=line; j++)
		{
			scanf("%d", &weight);
				path[i][j] = weight;
				visit[i][j] = false;
		}
	}
}
int main()
{
	//freopen("read.txt", "r", stdin);
	int T;
	scanf("%d", &T);
	int co = 1;
	while(T--)
	{
		int n;
		scanf("%d", &n);
		result = n*n -n;
		input(n);
		int tep = floyd(n);
		
		printf("Case %d: ", co++);
		if(tep == 0)
		printf("impossible\n");
		else
		{
			printf("%d\n", result);
		}
	}
	return 0;
}

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