（并查集） Wireless Network --POJ --2236

链接：

http://poj.org/problem?id=2236

http://acm.hust.edu.cn/vjudge/contest/view.action?cid=82830#problem/A

代码：

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<math.h>
#include<algorithm>
#include<iostream>
using namespace std;

#define N 1005

int n, f[N], a[N][2], repair[N];

int Find(int x)
{
    if(f[x]!=x)
        f[x] = Find(f[x]);
    return f[x];
}

double Dis(int x, int y)
{
    return sqrt(double((a[x][0]-a[y][0])*(a[x][0]-a[y][0])+(a[x][1]-a[y][1])*(a[x][1]-a[y][1])));
}

int main()
{
    double d;
    int i, x, y, len=0;
    char ch;

    memset(repair, 0, sizeof(repair));
    memset(a, 0, sizeof(a));

    scanf("%d%lf", &n, &d);

    for(i=0; i<n; i++)
    {
        f[i]=i;
        scanf("%d%d", &a[i][0], &a[i][1]);
    }
    f[n]=n;

    while(cin>>ch)
    {
        if(ch=='O')
        {
            scanf("%d", &x);
            x--;
            repair[len++]=x;
            for(i=0; i<len-1; i++)
            {
                if(repair[i]!=x && Dis(repair[i], x)<=d)
                    f[Find(repair[i])]=Find(x);
            }
        }
        if(ch=='S')
        {
            scanf("%d%d", &x, &y);
            x--, y--;

            if(Find(x)==Find(y))
                printf("SUCCESS
");
            else
                printf("FAIL
");
        }
    }

    return 0;
}