并查集+几何——pku2236

把点与点的关系保存在连接矩阵里就好了，如果距离小于等于规定距离的话就赋值为1

然后不断做（做符合条件）合并操作即可……

#include<stdio.h>

#define N 1005
int f[N];
int d;
int ji[N];

struct data 
{
    int x,y;
}p[N];

bool map[N][N];

int dis(data a,data b)
{
    int temp=(a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y);
    if(temp<=(d*d))
    return 1;
    return 0;
}

int find(int pos)
{
    if(f[pos]==-1)return pos;
    return pos=find(f[pos]);
}

int un(int x,int y)
{
    int a=find(x);
    int b=find(y);
    if(a==b)return 0;
    f[a]=b;
    return 1;
}

int main()
{
    int n;
    scanf("%d%d",&n,&d);
    int i,j;
    for(i=1;i<=n;i++)
    {
        f[i]=-1;
        scanf("%d%d",&p[i].x,&p[i].y);
    }

    for(i=1;i<=n;i++)
    {
        for(j=i;j<=n;j++)
        {
            if(i==j) 
            {
                map[i][i]=0;
                continue;
            }
            map[i][j]=dis(p[i],p[j]);
            map[j][i]=map[i][j];
        }
    }
    getchar();
    char rt;
    int add=0,temp,a,b;
    while(scanf("%c",&rt)!=EOF)
    {
        if(rt=='O')
        {
            scanf("%d",&temp);
            for(i=1;i<=add;i++)
            {
                if(map[ji[i]][temp]==1)
                un(ji[i],temp);
            }
            add++;
            ji[add]=temp;
        }
        else if(rt=='S')
        {
            scanf("%d%d",&a,&b);
            if(find(a)==find(b))
                printf("SUCCESS\n");
            else
                printf("FAIL\n");
        }
        //getchar();
    }


}