ZOJ Problem Set - 3708 Density of Power Network

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemCode=3708

#include <stdio.h>
#include <string.h>
int main(int argc, char *argv[])
{
	int T,i,j,lineSum;
	int N,M;
	int x[505],y[505];
	int lineL [505][505] ;

	scanf("%d",&T);
	for(i = 0 ; i < T ;i++){
		lineSum = 0;
		scanf("%d %d",&N,&M); 

		memset (lineL,0,sizeof(lineL));
		memset (lineL,0,sizeof(x));
		memset (lineL,0,sizeof(y));

		for(j = 0 ; j < M ;j++){
			scanf("%d",&x[j]);
		}
		for(j = 0 ; j < M ;j++){
			scanf("%d",&y[j]);
		}
		for(j = 0 ; j < M ;j++){
			if(lineL[x[j]][y[j]] == 0 && lineL[y[j]][x[j]] == 0){

				lineSum ++;
				lineL[x[j]][y[j]]=lineL[y[j]][x[j]]=1;	

			}
		}
		printf("%.3f\n",lineSum/(N*1.0));
	} 

	return 0;
}