poj 2236

並查集應用的簡單題。對於每一個修好的電腦，我們遍歷所有已經修好的電腦，如果它們之間的距離小於等於d,那麼我們就將兩個集合合併到一起，在詢問是否能夠互通時，就看它們是否屬於同一個集合，但是我們不能寫成fa[x] == fa[y]，而應該寫成find(x)==find(y),因爲有可能有些節點並沒有進行路徑壓縮，進而也沒有在同一個集合中，所以我們得再壓縮一下。

#include<stdio.h>
#include<iostream>
#include<string>
#include<string.h>
#include<algorithm>
#include<iomanip>
#include<vector>
#include<time.h>
#include<queue>
#include<stack>
#include<iterator>
#include<math.h>
#include<stdlib.h>
#include<limits.h>
#include<map>
#include<set>
#include<bitset>
//#define ONLINE_JUDGE
#define eps 1e-5
#define INF 0x7fffffff
#define FOR(i,a) for((i)=0;i<(a);(i)++)
#define MEM(a) (memset((a),0,sizeof(a)))
#define sfs(a) scanf("%s",a)
#define sf(a) scanf("%d",&a)
#define sfI(a) scanf("%I64d",&a)
#define pf(a) printf("%d\n",a)
#define pfI(a) printf("%I64d\n",a)
#define pfs(a) printf("%s\n",a)
#define sfd(a,b) scanf("%d%d",&a,&b)
#define sft(a,b,num) scanf("%d%d%d",&a,&b,&num)
#define for1(i,a,b) for(int i=(a);i<b;i++)
#define for2(i,a,b) for(int i=(a);i<=b;i++)
#define for3(i,a,b)for(int i=(b);i>=a;i--)
#define MEM1(a) memset(a,0,sizeof(a))
#define MEM2(a) memset(a,-1,sizeof(a))
#define ll __int64
const double PI=acos(-1.0);
template<class T> T gcd(T a,T b){return b?gcd(b,a%b):a;}
template<class T> T lcm(T a,T b){return a/gcd(a,b)*b;}
template<class T> inline T Min(T a,T b){return a<b?a:b;}
template<class T> inline T Max(T a,T b){return a>b?a:b;}
using namespace std;
//#pragma comment(linker,"/STACK:1024000000,1024000000")
int n,m,d;
#define N 200005
#define M 100000
#define Mod 1000000000
#define p(x,y) make_pair(x,y)
const int MAX_len=550;
int fa[1024];
struct Node{
    int id,x,y,flag;
}a[1024];
vector<int> v;
bool check(int i,int j){
    int dist = (a[i].x-a[j].x)*(a[i].x-a[j].x)+(a[i].y-a[j].y)*(a[i].y-a[j].y);
    return dist <= d*d;
}
int findfa(int x){
    return x==fa[x]?fa[x]:fa[x]=findfa(fa[x]);
}
void Union(int x,int y){
    int fx = findfa(x);
    int fy = findfa(y);
    if(fx!=fy){
        if(fx<fy)
            fa[fy] = fx;
        else
            fa[fx] = fy;
    }
}
int main(){
#ifndef ONLINE_JUDGE
    freopen("in.txt", "r", stdin);
//  freopen("out.txt", "w", stdout);
#endif
    while(scanf("%d%d",&n,&d)!=EOF){
        for(int i=1;i<=n;i++){
            fa[i]=i;
            sfd(a[i].x,a[i].y);
            a[i].id=i;
            a[i].flag=0;
        }
        char op[2];
        int p,q;
        while(scanf("%s%d",op,&p)!=-1){
            if(op[0] == 'O'){
                a[p].flag=1;
                for(int j=1;j<=n;j++){
                    if(a[j].flag==0 || p == j) continue;
                    if(check(p,j)){
                        Union(p,j);
                    }
                }
            }else if(op[0] == 'S'){
                scanf("%d",&q);
                if(findfa(p) == findfa(q))      //不能寫成fa[p] == fa[q];
                    printf("SUCCESS\n");
                else
                    printf("FAIL\n");
            }
        }
    }
    return 0;
}