[Cogs14] [网络流24题#1] 飞行员分配方案 [网络流，最大流，二分图匹配]

经典二分图匹配，可以用匈牙利算法，也可以用最大流

代码如下（Dinic）：

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <ctime>
#include <algorithm>
#include <queue>using namespace std;template<const int _n>
struct Edge
{struct Edge_base { int    to,next,w; }e[_n]; int    p[_n],cnt;void    insert(const int x,const int y,const int z){ e[++cnt].to=y; e[cnt].next=p[x]; e[cnt].w=z; p[x]=cnt; return ; }int    start(const int    x) { return p[x]; }void    clear() { cnt=1;memset(p,0,sizeof(p)); }Edge_base&    operator[](const int x) { return e[x]; }
};int    n,m,flow,SSS,TTT;
int    level[110],From[110],From_e[110];
Edge<310>    e;bool    Bfs(const int S)
{int    i,t;queue<int>    Q;memset(level,0,sizeof(level));memset(From,0,sizeof(From));level[S]=1;Q.push(S);while(!Q.empty()){t=Q.front(),Q.pop();for(i=e.start(t);i;i=e[i].next){if(!level[e[i].to] && e[i].w){level[e[i].to]=level[t]+1;Q.push(e[i].to);From[e[i].to]=t;From_e[e[i].to]=i;if(e[i].to==TTT)goto End;}}}
End:if(!level[TTT])return false;flow++;for(i=TTT;i!=SSS;i=From[i])e[From_e[i]].w--,e[From_e[i]^1].w++;return true;
}int    Dinic()
{while(Bfs(SSS));return flow;
}int main()
{freopen("flyer.in","r",stdin);freopen("flyer.out","w",stdout);int    i,x,y;scanf("%d%d",&m,&n);m=m-n;while(scanf("%d%d",&x,&y)==2){if(x>y)swap(x,y);e.insert(x,y,1);e.insert(y,x,0);}SSS=n+m+1,TTT=n+m+2;for(i=1;i<=n;++i){e.insert(SSS,i,1);e.insert(i,SSS,0);}for(i=n+1;i<=m+n;++i){e.insert(i,TTT,1);e.insert(TTT,i,0);}printf("%d\n",Dinic());return 0;
}