二分图匈牙利模板

  1 #include <bits/stdc++.h>
  2  
  3 using namespace std;
  4 const int maxn = 55;
  5 const int maxm = 3000;
  6 int n,m,k;
  7 int vis[maxm],Left[maxm];
  8 int mark[maxn][maxn];
  9 bool ok[maxn][maxn];
 10 int id[maxn][maxn];
 11 vector<int> l[maxm];
 12 set<int>up;
 13 int getid (int xx,int yy)
 14 {
 15     return (xx-1)*m+yy;
 16 }
 17 bool check (int xx,int yy)
 18 {
 19     if (xx>=1&&xx<=n&&yy>=1&&yy<=m&&ok[xx][yy])
 20         return true;
 21     else
 22         return false;
 23 }
 24 void add (int x,int y)
 25 {
 26     l[x].push_back(y);
 27     l[y].push_back(x);
 28 }
 29 int dfs (int x)
 30 {
 31     for (int i=0;i<l[x].size();++i){
 32         int it = l[x][i];
 33         if(Left[it]==-1){
 34             Left[it] = x;
 35             return 1;
 36         }
 37         if (vis[it]) continue;
 38         vis[it] = 1;
 39         if(dfs(Left[it])){
 40             Left[it] = x;
 41             return 1;
 42         }
 43     }
 44     return 0;
 45 }
 46  
 47 int main()
 48 {
 49     //freopen("de.txt","r",stdin);
 50     while (~scanf("%d%d",&n,&m)){
 51     memset(ok,true,sizeof ok);
 52     memset(Left,-1,sizeof Left);
 53     scanf("%d",&k);
 54     for (int i=0;i<k;++i){
 55         int xx,yy;
 56         scanf("%d%d",&xx,&yy);
 57         ok[xx][yy] = false;
 58     }
 59     for (int i=1;i<=n;++i){
 60         int j;
 61         if (i%2) j=1;
 62         else j=2;
 63         for (;j<=m;j+=2){
 64             if (check(i,j)){
 65                 //printf("%d %d\n",i,j);
 66                 int id = getid(i,j);
 67                 if (check(i+1,j)){
 68                     int id2 = getid(i+1,j);
 69                     add(id,id2);
 70                 }
 71                 if (check(i,j+1)){
 72                     int id2 = getid(i,j+1);
 73                     add(id,id2);
 74                 }
 75                 if (check(i-1,j)){
 76                     int id2 = getid(i-1,j);
 77                     add(id,id2);
 78                 }
 79                 if (check(i,j-1)){
 80                     int id2 = getid(i,j-1);
 81                     add(id,id2);
 82                 }
 83             }
 84         }
 85     }
 86     int ans = 0;
 87     for (int i=1;i<=n;++i){
 88         int j;
 89         if (i%2) j=1;
 90         else j=2;
 91         for (;j<=m;j+=2){
 92             if (check(i,j)){
 93                 memset(vis,0,sizeof vis);
 94                 int id = getid(i,j);
 95                 ans += dfs(id);
 96             }
 97         }
 98     }
 99     printf("%d\n",ans);
100     }
101     return 0;
102 }