POJ 1789

做题的感受，稠密图的MST问题还是推荐使用Prim算法，尤其是这种完全图，直接设置dist函数计算距离而非实现构建好一个数组计算时间上没什么差别（此题）空间上优化

#include <iostream>
#include <algorithm>
#include <queue>
#include <string>
#include <vector>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <string>
#include <stack>
#include <map>
#include <set>
using namespace std;

const int maxn= 2005;
const int l_code= 8;
const int INF= 0x3f3f3f3f;
char codes[maxn][l_code];
int vis[maxn], dis[maxn];

int Dist(const int i, const int j)
{
	if (i== j){
		return 0;
	}
	int ret= 0;
	for (int k= 0; k< l_code; ++k){
		if (codes[i][k]!= codes[j][k]){
			++ret;
		}
	}

	return ret;
}
int Prim(const int n)
{
	memset(vis, 0, sizeof(vis));
	dis[0]= 0;
	vis[0]= 0;
	for (int i= 1; i< n; ++i){
		dis[i]= Dist(0, i);
	}
	int ans= 0;
	int minc, p;
	int t;

	for (int i= 1; i< n; ++i){
		minc= INF;
		p= -1;
		for (int j= 1; j< n; ++j){
			if (!vis[j] && dis[j]< minc){
				minc= dis[j];
				p= j;
			}
		}
		if (-1== p){
			return -1;
		}
		ans+= minc;
		vis[p]= 1;
		for (int j= 1; j< n; ++j){
			if (!vis[j] && dis[j]> (t= Dist(p, j))){
				dis[j]= t;
			}
		}
	}

	return ans;
}
int main()
{
	int n;
	while (~scanf("%d", &n) && n){
		for (int i= 0; i< n; ++i){
			scanf(" %s" ,codes[i]);
		}
		printf("The highest possible quality is 1/%d.\n", Prim(n));
	}

	return 0;
}