COGS14. [网络流24题] 搭配飞行员

 1 /*by SilverN*/
 2 #include<iostream>
 3 #include<algorithm>
 4 #include<cstring>
 5 #include<cstdio>
 6 #include<cmath>
 7 #include<queue>
 8 using namespace std;
 9 const int mxn=300;
10 int read(){
11     int x=0,f=1;char ch=getchar();
12     while(ch<‘0‘ || ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
13     while(ch>=‘0‘ && ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}
14     return x*f;
15 }
16 struct edge{
17     int v,nxt,f;
18 }e[mxn*mxn*2];
19 int hd[mxn],mct=1;
20 void add_edge(int u,int v,int c){
21     e[++mct].v=v;e[mct].f=c;e[mct].nxt=hd[u];hd[u]=mct;return;
22 }
23 void insert(int u,int v,int c){
24     add_edge(u,v,c);add_edge(v,u,0);return;
25 }
26 int n,m,S,T;
27 int d[mxn];
28 bool BFS(){
29     memset(d,0,sizeof d);
30     d[S]=1;
31     queue<int>q;
32     q.push(S);
33     while(!q.empty()){
34         int u=q.front();q.pop();
35         for(int i=hd[u];i;i=e[i].nxt){
36             int v=e[i].v;
37             if(!d[v] && e[i].f){
38                 d[v]=d[u]+1;q.push(v);
39             }
40         }
41     }
42     return d[T];
43 }
44 int DFS(int u,int lim){
45     if(u==T)return lim;
46     int tmp,f=0;
47     for(int i=hd[u];i;i=e[i].nxt){
48         int v=e[i].v;
49         if(d[v]==d[u]+1 && e[i].f){
50             tmp=DFS(v,min(lim,e[i].f));
51             e[i].f-=tmp;
52             e[i^1].f+=tmp;
53             lim-=tmp;
54             f+=tmp;
55             if(!lim)return f;
56         }
57     }
58     d[u]=0;
59     return f;
60 }
61 int Dinic(){
62     int res=0;
63     while(BFS())res+=DFS(S,1e9);
64     return res;
65 }
66 int main(){
67     freopen("flyer.in","r",stdin);
68     freopen("flyer.out","w",stdout);
69     scanf("%d%d",&n,&m);
70     S=0;T=n+1;
71     int i,j;
72     for(i=1;i<=m;i++){insert(S,i,1);}
73     for(i=m+1;i<=n;i++){insert(i,T,1);}
74     int a,b;
75     while(scanf("%d%d",&a,&b)!=EOF){
76         insert(a,b,1);
77     }
78     int ans=Dinic();
79     printf("%d\n",ans);
80     return 0;
81 }