ZOJ 1914 Arctic Network (kruskal + prim )

#include<iostream>
#include<string>
#include<queue>
#include<cmath>
#include<stack>
using namespace std;
struct edge
{
int from,to;
int w;
} t;
int point[501][2],p[501];
int find(int i)
{   return p[i]==i?i:(p[i]=find(p[i])); }
struct cmp
{
bool operator ()(const struct edge a,const struct edge b)
{
return a.w>b.w;
}
};
int main(void)
{
int cases,from,to,i,j;
int satelite,n;
double len;
priority_queue<edge,vector<edge>,cmp> q;
stack<int> qq;
cin >> cases;
while( cases-- )
{
while( !q.empty() ) q.pop();
cin >> satelite >> n;
for( i = 1; i <= n; i++ )
cin >> point[i][0] >> point[i][1];
for( i = 1; i <= n; i++ )
for( j = i+1; j <= n; j++ )
{
t.from = i;
t.to = j;
t.w = (point[i][0]-point[j][0])*(point[i][0]-point[j][0])
+ (point[i][1]-point[j][1])*(point[i][1]-point[j][1]);
q.push(t);
}
while( !qq.empty() ) qq.pop();

for( i = 1; i<= n; i++ ) p[i] = i;
while( !q.empty() )
{
t = q.top();q.pop();
from = find( t.from );
to = find( t.to );
if( from == to ) continue;
p[from] = to;
qq.push(t.w);
}
while( --satelite )
qq.pop();
len = sqrt( qq.top() );
printf("%.2f/n",len);
}
return 0;
}

#include<iostream>
#include<string>
#include<queue>
#include<cmath>
#include<stack>
#include<cstring>
using namespace std;
const int M = 501;
const int INF = 99999999;
int mat[M][M],flag[M],dist[M];
int point[M][2];
typedef pair<int,int> pii;
priority_queue<pii,vector<pii>,greater<pii> > q;
priority_queue<int> qq;
int main(void)
{
int cases,n,m;
int i,j,now;
cin >> cases;
while( cases-- )
{
while(!qq.empty() ) qq.pop();
memset(mat,0,sizeof(mat));
memset(flag,0,sizeof(flag));
cin >> m >> n;
for( i = 1; i <= n; i++ )
cin >> point[i][0] >> point[i][1];

for( i = 1; i <= n; i++ )
for( j = i+1; j <= n; j++ )
mat[i][j] = mat[j][i]= (point[i][0]-point[j][0])*(point[i][0]-point[j][0])
+ (point[i][1]-point[j][1])*(point[i][1]-point[j][1]);

for( i =1; i <= n; i++ ) dist[i]=INF;
dist[now=1] = 0;
q.push( make_pair(0,1) );
while( !q.empty() )
{
pii t = q.top();q.pop();
now = t.second;
if( flag[now] ) continue;
flag[now] = 1;
qq.push(t.first);
for( i = 1;i <= n; i++ )
if( !flag[i] && dist[i] > mat[now][i] && now !=i)
{
dist[i] = mat[now][i];
q.push( make_pair(dist[i],i) );
}
}
while( --m )    qq.pop();
printf("%.2f/n",sqrt( qq.top() ));
}
return 0;
}