poj 1751 highways

#include<iostream>
using namespace std;

struct town{
int x;
int y;
}town[800];

struct dist{
int from;
int to;
int dis;
int vis;
}dist[320000];

int cmp(const void *a, const void *b)
{
return (*(struct dist *)a).dis > (*(struct dist *)b).dis ? 1 : -1;
}

int fa[800];
int find(int x)
{
if(x == fa[x])
return x;
fa[x] = find(fa[x]);
return fa[x];
}

int main()
{
int N, M, i;
cin>>N;
for(i=0;i<N;i++)
{
cin>>town[i].x>>town[i].y;
}

cin>>M;
for(i=0;i<M;i++)
{
cin>>dist[i].from>>dist[i].to;
dist[i].dis = 0;
dist[i].vis = 0;
}

int j, k;
i = M;
for(j=0;j<N;j++)
{
for(k=j+1;k<N;k++)
{

dist[i].vis = 1;
dist[i].from = j+1;
dist[i].to = k + 1;
dist[i].dis = (town[j].x-town[k].x)*(town[j].x-town[k].x) + (town[j].y-town[k].y)*(town[j].y-town[k].y);
i++;
}
}

int num = M+N*(N-1)/2;
qsort(dist, num, sizeof(dist[0]), cmp);

for(i=1;i<=N;i++)
fa[i]=i;

int count = 0;
for(i=0;i<num;i++)
{
if(find(dist[i].from) != find(dist[i].to))
{
fa[find(dist[i].from)] = find(dist[i].to);
count++;
if(dist[i].vis)
cout<<dist[i].from<<" "<<dist[i].to<<endl;

if(count == N-1)
break;
}
}

system("pause");
return 0;
}

#include<iostream>
#include<climits>
#include<cstring>
using namespace std;

struct node{
int x, y;
}node[755];

int maxEdge=INT_MAX;
int flag[755];
int pre[755];
int dist[755];

int map[755][755];
int main()
{
int N, M;
cin>>N;
for(int i=1;i<=N;i++)
{
cin>>node[i].x>>node[i].y;
}
memset(map, 0, sizeof(map));
for(int i=1;i<=N;i++)
{
for(int j=1;j<=N;j++)
{
map[i][j]=(node[i].x-node[j].x)*(node[i].x-node[j].x)+(node[i].y-node[j].y)*(node[i].y-node[j].y);
}
}
for(int i=0;i<=N;i++)
{
flag[i]=0;
dist[i]=maxEdge;
pre[i]=1;
}

cin>>M;
for(int i=1;i<=M;i++)
{
int a, b;
cin>>a>>b;
pre[b] = a;
map[a][b]=0;
map[b][a]=0;
}

flag[1]=1;
dist[1]=maxEdge;
for(int j=2;j<=N;j++)
{
dist[j]=map[1][j];
}

int next,p=1;
for(int i=1;i<N;i++)
{
int min=maxEdge;

for(int j=1;j<=N;j++)
{
if(dist[j]<min)
{
min=dist[j];
next = j;
}
}
p=pre[next];
flag[next]=1;
dist[next]=maxEdge;
pre[next]=p;
if(map[pre[next]][next]  != 0)
{
cout<<pre[next]<<" "<<next<<endl;
}
for(int j=1;j<=N;j++)
{
if((map[next][j] < dist[j])&& flag[j]==0)
{
dist[j]=map[next][j];
pre[j]=next;
}
}

}
system("pause");
return 0;
}