hdu 1875 最小生成树(kruskal)

/*
题意：中文题

题解：赤裸裸的最小生成树
*/
#include <cstdio>
#include <cmath>
#include <algorithm>

const int MAXN = 109;
const int MAXE = 10009;

struct edge
{
int u, v;
double w;
bool vis;
}E[MAXE];

int set[MAXN];
int N, EN, sum;

void addedge(int u, int v, double w)
{
E[ EN ].u = u;
E[ EN ].v = v;
E[ EN ].w = w;
E[ EN ].vis = false;
EN++;
return ;
}

void init()
{
for (int i = 1; i <= N; i++) // 树的标号从1开始
set[i] = i;
return ;
}

int find(int x)
{
while (set[x] != x)
x = set[x];
return set[x];
}

bool cmp(edge a, edge b)
{
return a.w < b.w;
}

double kruskal()
{
int x, y;
double ret;
init();
sum = 0;
ret = 0;
std::sort(E,E+EN,cmp);
for (int i = 0; i < EN && sum < N - 1; i++)
{
x = find( E[i].u );
y = find( E[i].v );
if (x == y)
continue;
set[x] = set[y];
E[i].vis = true;
sum++;
ret += E[i].w;
}
return ret;
}

struct point
{
int x,y;
}P[MAXN];

int getdisSq(point a, point b)
{
return (a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y);
}

int main(void)
{
int t;
scanf("%d",&t);
while (t--)
{
scanf("%d",&N);
for(int i=1; i<=N; i++)
scanf("%d%d",&P[i].x,&P[i].y);
EN = 0;
for(int i=1; i<N; i++)
{
for(int j=i+1; j<=N; j++)
{
int tmp = getdisSq(P[i],P[j]);
if (100 <= tmp && tmp <= 1000000)
addedge(i,j,sqrt(1.0*tmp));
}
}
double ans = kruskal();
if (sum == N-1)
printf("%.1lf\n",100*ans);
else
printf("oh!\n");
}
return 0;
}