POJ 2536 最大匹配入门

最新推荐文章于 2019-08-10 21:11:00 发布

最新推荐文章于 2019-08-10 21:11:00 发布 · 308 阅读

本文介绍了一种算法，旨在解决gopher家族面对猎鹰威胁时如何通过最优策略最小化被捕食的风险。该算法考虑了gopher与洞穴的位置、速度等参数，利用匹配算法来确定哪些gopher能成功进入洞穴避难。

Gopher II

Time Limit: 2000MS		Memory Limit: 65536K
Total Submissions: 3680		Accepted: 1539

Description

The gopher family, having averted the canine threat, must face a new predator.

The are n gophers and m gopher holes, each at distinct (x, y) coordinates. A hawk arrives and if a gopher does not reach a hole in s seconds it is vulnerable to being eaten. A hole can save at most one gopher. All the gophers run at the same velocity v. The gopher family needs an escape strategy that minimizes the number of vulnerable gophers.

Input

The input contains several cases. The first line of each case contains four positive integers less than 100: n, m, s, and v. The next n lines give the coordinates of the gophers; the following m lines give the coordinates of the gopher holes. All distances are in metres; all times are in seconds; all velocities are in metres per second.

Output

Output consists of a single line for each case, giving the number of vulnerable gophers.

Sample Input

2 2 5 10
1.0 1.0
2.0 2.0
100.0 100.0
20.0 20.0

Sample Output

Source

Waterloo local 2001.01.27

敲错了一个变量，让我WA了很久都没看出来。。

Source Code

Problem: 2536		User: bingshen
Memory: 748K		Time: 32MS
Language: G++		Result: Accepted

Source Code

#include<stdio.h>
#include<algorithm>
#include<string.h>
#include<math.h>
#include<vector>

using namespace std;

struct Point
{
	double x;
	double y;
};

Point p1[105];
Point p2[105];
vector<int>map[105];
int link[105];
bool cover[105];
int n,m;

void init()
{
	memset(link,-1,sizeof(link));
	memset(map,0,sizeof(map));
}

double dis(Point a,Point b)
{
	return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y));
}

void makemap(int s,int v)
{
	int i,j;
	double r;
	r=s*v;
	for(i=0;i<n;i++)
		for(j=0;j<m;j++)
		{
			if(dis(p1[i],p2[j])<=r)
				map[i].push_back(j);
		}
}

bool find(int v)
{
	int i;
	for(i=0;i<map[v].size();i++)
	{
		if(!cover[map[v][i]])
		{
			cover[map[v][i]]=true;
			if(link[map[v][i]]==-1||find(link[map[v][i]]))
			{
				link[map[v][i]]=v;
				return true;
			}
		}
	}
	return false;
}

int main()
{
	int i,life;
	double s,v;
	while(scanf("%d%d%lf%lf",&n,&m,&s,&v)!=EOF)
	{
		init();
		life=0;
		for(i=0;i<n;i++)
			scanf("%lf%lf",&p1[i].x,&p1[i].y);
		for(i=0;i<m;i++)
			scanf("%lf%lf",&p2[i].x,&p2[i].y);
		makemap(s,v);
		for(i=0;i<n;i++)
		{
			memset(cover,0,sizeof(cover));
			if(find(i))
				life++;
		}
		printf("%d/n",n-life);
	}
	return 0;
}