可能因为很长时间不敲网络流所以现在SB题都写得卡(关键是自己的板子里埋了不少坑考场上就崩掉了) 全当是复习吧
二分图匹配裸题
#include <bits/stdc++.h>
using namespace std;
const int N = 100005, MAXN = 100005;
#define reset(x) memset(x,0,sizeof x)
struct graph {
int n,m,M,S,T,head[N],cur[N],dep[N],gap[N],q[N];
long long ans;
struct ed {
int to,nxt,val;
} edge[MAXN];
void init(int n0,int m0,int S0,int T0) {
n=n0,m=m0,S=S0,T=T0,M=1,reset(gap);
reset(head),reset(cur),reset(dep),reset(q);
}
void mk(int u,int v,int w) {
edge[++M]=(ed) {v,head[u],w},head[u]=M;
}
void make(int u,int v,int w) {
mk(u,v,w); mk(v,u,0);
}
int dfs(int u,int mx) {
if (u==T)
return mx;
int num=0,f;
for (int &i=cur[u],v; i; i=edge[i].nxt)
if (dep[v=edge[i].to]==dep[u]-1 && (f=edge[i].val))
if (edge[i].val-=(f=dfs(v,min(mx-num,f))), edge[i^1].val+=f, (num+=f)==mx)
return num;
if (!--gap[dep[u]++])
dep[S]=n+1;
return ++gap[dep[u]],cur[u]=head[u],num;
}
void solve() {
for (int i=1; i<=n; ++i)
cur[i]=head[i];
ans=0;
for (gap[0]=n; dep[S]<=n; ans+=dfs(S,0x7fffffff));
}
} g;
int n,m,t1,t2;
int main()
{
cin>>t1>>t2;
n=t2; m=t1-t2;
g.init(n+m+2,0,n+m+1,n+m+2);
while(cin>>t1>>t2) g.make(t1,t2,1);
for(int i=1;i<=n;i++) g.make(n+m+1,i,1);
for(int i=1;i<=m;i++) g.make(i+n,n+m+2,1);
g.solve();
cout<<g.ans<<endl;
}