【最小路径覆盖】BZOJ2150-部落战争

 1 #include<bits/stdc++.h>
 2 using namespace std;
 3 const int MAXN=55;
 4 int m,n,r,c,maps[MAXN][MAXN];
 5 int lk[MAXN*MAXN],vis[MAXN*MAXN];
 6 vector<int> E[MAXN*MAXN];
 7 
 8 int check(int x,int y)
 9 {
10     if (x>=1 && x<=m && y>=1 && y<=n && maps[x][y]) return 1;else return 0;
11 }
12 
13 int id(int x,int y){return ((x-1)*n+y);}
14 
15 void addedge(int u,int v)
16 {
17     E[u].push_back(v);
18 }
19 
20 int find(int u)
21 {
22     for (int i=E[u].size()-1;i>=0;i--)
23     {
24         int v=E[u][i];
25         if (!vis[v])
26         {
27             vis[v]=1;
28             if (!lk[v]|| find(lk[v]))//呜哇这里写成了find(v)半天没有发现，果然是老阿姨了啊 
29             {
30                 lk[v]=u;
31                 return 1;
32             }
33         }
34     }
35     return 0;
36 }
37 
38 void init()
39 {
40     scanf("%d%d%d%d",&m,&n,&r,&c);
41     for (int i=1;i<=m;i++)
42     {
43         char str[MAXN];
44         scanf("%s",str);
45         for (int j=0;j<n;j++)
46             if (str[j]==‘.‘) maps[i][j+1]=1;else maps[i][j+1]=0;
47     }
48     for (int i=1;i<=m;i++)
49         for (int j=1;j<=n;j++)
50             if (maps[i][j])
51             {
52                 if (check(i+r,j+c)) addedge(id(i,j),id(i+r,j+c));
53                 if (check(i+r,j-c)) addedge(id(i,j),id(i+r,j-c));
54                 if (check(i+c,j+r))    addedge(id(i,j),id(i+c,j+r));
55                 if (check(i+c,j-r)) addedge(id(i,j),id(i+c,j-r));
56             }
57 }
58 
59 void solve()
60 {
61     memset(lk,0,sizeof(lk));
62     int sum=0,ans=0;
63     for (int i=1;i<=m;i++)
64         for (int j=1;j<=n;j++)
65         {
66             if (maps[i][j]==1)
67             {
68                 int x=id(i,j);
69                 memset(vis,0,sizeof(vis));
70                 sum++;
71                 if (find(x)) ans++;
72             }
73         }
74     printf("%d",sum-ans);
75 }
76 
77 int main()
78 {
79     init();
80     solve();
81 }