匈牙利算法

Posted 2020-10-05 ovo

看到了一篇有趣的博客：http://blog.csdn.net/dark_scope/article/details/8880547

#include<algorithm>
#include<iostream>
#include<cstdlib>
#include<cstdio>
#define ma 1005
bool used[ma];
int pre[1000005],fir[1000005],nxt[1000005],to[1000005],n,m,e=0;
using namespace std;
int get()
{
	int ans=0,f=1;char ch=getchar();
	while(!isdigit(ch)) {if(ch==‘-‘) f=-1;ch=getchar();}
	while(isdigit(ch)) {ans=ans*10+ch-‘0‘;ch=getchar();}
	return ans*f;
}
inline void add(int a,int b)
{
	nxt[++e]=fir[a];fir[a]=e;to[e]=b;
}
bool find(int x)
{
	for(register int i=fir[x];i;i=nxt[i])
	  if(!used[to[i]])
	  {
	  	used[to[i]]=1;
	  	if(!pre[to[i]]||find(pre[to[i]]))
	  	{
	  		pre[to[i]]=x;
	  		return 1;
		}
	  }
	return 0;
}
int main()
{
	n=get(),m=get();
	int u,v,e=get(),ans=0;
	for(register int i=1;i<=e;i++)
	{
		u=get();v=get();
		if(u>n||v>m)
		  continue;
		add(u,v);
	}
	for(register int i=1;i<=n;i++)
	{
		if(find(i))
		  ans++;
		fill(used,used+m+1,0);
	}
	printf("%d",ans);
	return 0;
}