poj2421(prim算法)

用邻接表一直WA，只好改用邻接矩阵。
贴代码

#include<iostream>
#include<vector>
#include<queue>
#include<string>
using namespace std;
char str[2010][8];
int mark[2010];          //标记是否访问过，访问过为1，否则为0
int map[2002][2002];
	int n;
class Dist
{
public:
	int pre;
	int length;
	int index;
	friend bool operator<(const Dist &a,const Dist &b)
	{
		return a.length>b.length;
	}
};

void prim(int s)
{
	int ans=0;
	Dist *D = new Dist[n+1];
	for(int i=1;i<=n;i++)
	{
		D[i].index = i;
		D[i].pre = s;
		D[i].length = 1<<30;
	}
	priority_queue<Dist> aqueue;
	int now_node=s;

	for(int i=1;i<n;i++)
	{
		mark[now_node]=1;
		for(int j=1;j<=n;j++)
		{
			if(  mark[j]==0 && D[j].length>map[now_node][j])
			{
				D[j].length = map[now_node][j];
				D[j].pre = now_node;
				aqueue.push(D[j]);
			}
		}
		Dist d;
		while(!aqueue.empty())
		{
			d = aqueue.top();
			aqueue.pop();
			if(mark[d.index]==0)
				break;
		}

		
		now_node = d.index;
		ans = ans + d.length;
	}
	cout<<"The highest possible quality is 1/"<<ans<<"."<<endl;
}

int different(int s1,int s2)
{
	int ans=0;
	for(int i=0;i<7;i++)
	{
		if(str[s1][i]!=str[s2][i])
			ans++;
	}
	return ans;
}
int main()
{
	int i,j;

	int weight;
	while(cin>>n)
	{
		if(n==0)
			break;

		memset(mark,0,sizeof(mark));
		for(i=1;i<=n;i++)
		{
			scanf("%s",str[i]);
		}

		for(i=1;i<=n;i++)
		{
			for(j=1;j<i;j++)
			{
				weight=different(i,j);
				map[i][j]=map[j][i]=weight;

			}
		}
		prim(1);
	}

	return 0;
}