uva live 6827 Galaxy collision

Posted 2020-09-26 mthoutai

就是给出非常多点，要求分成两个集合，在同一个集合里的点要求随意两个之间的距离都大于5。

求一个集合。它的点数目是全部可能答案中最少的。

直接从随意一个点爆搜，把它范围内的点都丢到跟它不一样的集合里。不断这样搞即可了。

由于可能有非常多相离的远，把每次搜索得到的那个最小的数目加起来就可以。

因为全部点都格点上，所以仅仅须要枚举一个点可以包括的点是否在数据中存在就可以。

当然也能够用一棵树直接去找。这我并不会。。

时间复杂度是81nlogn

湖大的OJ机器太老。。

。还要开栈。

。

。UVA LIVE随便交就过了。

#include<map>
#include<string>
#include<cstring>
#include<cstdio>
#include<cstdlib>
#include<cmath>
#include<queue>
#include<vector>
#include<iostream>
#include<algorithm>
#include<bitset>
#include<climits>
#include<list>
#include<iomanip>
#include<stack>
#include<set>
using namespace std;
struct Point
{
      int x,y;
      Point(){}
      Point(int x,int y)
      {
            this->x=x;
            this->y=y;
      }
      bool operator <(Point one)const
      {
            if(x!=one.x)
                  return x<one.x;
            return y<one.y;
      }
};
vector<Point>bx;
int dis2(Point one,Point two)
{
      return (one.x-two.x)*(one.x-two.x)+(one.y-two.y)*(one.y-two.y);
}
void create()
{
      for(int i=-5;i<=5;i++)
            for(int j=-5;j<=5;j++)
                  if(dis2(Point(i,j),Point(0,0))<=25)
                        bx.push_back(Point(i,j));
}
map<Point,int>mp;
Point cnt;
void dfs(Point v)
{
      int n=bx.size(),no=mp[v];
	  map<Point,int>::iterator it;
      for(int i=0;i<n;i++)
      {
            Point t=Point(v.x+bx[i].x,v.y+bx[i].y);
            it=mp.find(t);
			if(it!=mp.end()&&it->second==0)
            {
                  if(no==1)
                  {
                  		it->second=2;
                        cnt.y++;
                  }
                  else
                  {
                        it->second=1;
                        cnt.x++;
                  }
                  dfs(t);
            }
      }
}
int main()
{
      //int size = 256 << 20; // 256MB
     // char *p = (char*) malloc (size) + size;
    //  __asm__ ("movl %0, %%esp\n" :: "r" (p) );
      create();
      int n;
      while(scanf("%d",&n)!=EOF)
      {
	      while(n--)
	      {
	            Point t;
	            scanf("%d%d",&t.x,&t.y);
	            mp[t]=0;
	      }
	      map<Point,int>::iterator it;
	      int ans=0;
	      for(it=mp.begin();it!=mp.end();it++)
	      {
	            if(it->second==0)
	            {
	                  it->second=1;
	                  cnt.x=1;
	                  cnt.y=0;
	                  dfs(it->first);
	                  if(cnt.x>cnt.y)
	                        swap(cnt.x,cnt.y);
	                    ans+=cnt.x;
	            }
	      }
	      cout<<ans<<endl;
      }
      return 0;
}

Time Limit: 15000ms, Special Time Limit:37500ms, Memory Limit:65536KB

Total submit users: 9, Accepted users: 6

Problem 13307 : No special judgement

Problem description

The Andromeda galaxy is expected to collide with our Milky Way in about 3.8 billion years. The collision will probably be a merging of the two galaxies, with no two stars actually colliding. That is because the distance between stars in both galaxies is so huge. Professor Andrew is building a computational model to predict the possible outcomes of the collision and needs your help! A set of points in the two dimensional plane is given, representing stars in a certain region of the already merged galaxies. He does not know which stars came originally from which galaxy; but he knows that, for this region, if two stars came from the same galaxy, then the distance between them is greater than 5 light years. Since every star in this region comes either from Andromeda or from the Milky Way, the professor also knows that the given set of points can be separated into two disjoint subsets, one comprising stars from Andromeda and the other one stars from the Milky Way, both subsets with the property that the minimum distance between two points in the subset is greater than 5 light years. He calls this a good separation, but the bad news is that there may be many different good separations. However, among all possible good separations there is a minimum number of stars a subset must contain, and this is the number your program has to compute.

Input

The first line contains an integer N (1 ≤ N ≤ 5×10^4) representing the number of points in the set. Each of the next N lines describes a different point with two integers X and Y (1 ≤ X,Y ≤ 5 × 10^5), indicating its coordinates, in light years. There are no coincident points, and the set admits at least one good separation.

Output

Output a line with an integer representing the minimum number of points a subset may have in a good separation.

Sample Input

Sample input 1 6 1 3 9 1 11 7 5 7 13 5 4 4 Sample input 2 2 10 10 50 30

Sample Output

Sample output 1 2 Sample output 2 0

Problem Source

ICPC Latin American Regional ? 2014