题目链接

戳我

\(solution\)

这道题和网络24题之骑士共存问题很相似
只是输入方式不一样而已
详细见:这儿

\(Code\)

#include<bits/stdc++.h>
#define file(a) freopen(a".in","r",stdin);freopen(a".out","w",stdout)
#define rg register
using namespace std;
typedef long long ll;
int n,m,s,t,z,y,x;
inline int read(){int x=0,f=1;char c=getchar();while(c<'0'||c>'9')  f= (c=='-')?-1:1,c=getchar();while(c>='0'&&c<='9')  x=x*10+c-48,c=getchar();return f*x;
}
struct node{int to,next,v;
}a[400001];
int cnt,head[200001],cur[200001];
void add(int x,int y,int c){a[++cnt].to=y;a[cnt].next=head[x];a[cnt].v=c;head[x]=cnt;
}
queue <int> q;
int dep[100001];
int bfs(){memset(dep,0,sizeof(dep));q.push(s),dep[s]=1;while(!q.empty()){int now=q.front();q.pop();for(int i=head[now];i;i=a[i].next){int v=a[i].to;if(!dep[v]&&a[i].v)q.push(v),dep[v]=dep[now]+1;}}if(dep[t]!=0)return 1;elsereturn 0;
}
int dfs(int k,int list){if(k==t)return list;for(int &i=cur[k];i;i=a[i].next){int v=a[i].to;if(a[i].v&&dep[v]==dep[k]+1){int p=dfs(v,min(list,a[i].v));if(p){a[i].v-=p;if(i%2)a[i+1].v+=p;elsea[i-1].v+=p;return p;}}}return 0;
}
int Dinic(){int ans=0;while(bfs()){for(int i=0;i<t;i++)cur[i]=head[i];int k=dfs(s,2147483);while(k)ans+=k,k=dfs(s,2147483);}return ans;
}
int f[201][201];
int fx[10]={0,1,1,-1,-1,2,2,-2,-2};
int fy[10]={0,2,-2,2,-2,1,-1,1,-1};
char S[1000];
int main(){n=read(),s=0,t=n*n+1;int sum=0;for(int i=1;i<=n;i++){cin>>S;for(int j=0;j<strlen(S);j++){f[i][j+1]=S[j]-'0';if(f[i][j+1])m++;}}for(int i=1;i<=n;i++)for(int j=1;j<=n;j++){if(f[i][j])continue;if(((i+j)%2)==0)add((i-1)*n+j,t,1),add(t,(i-1)*n+j,0);elseadd(s,(i-1)*n+j,1),add((i-1)*n+j,s,0);}for(int i=1;i<=n;i++)for(int j=1;j<=n;j++)for(int k=1;k<=8;k++){int x=i+fx[k],y=j+fy[k],p=(x-1)*n+y;if(x>0&&y>0&&x<=n&&y<=n&&((i+j)%2)==1&&!f[i][j]&&!f[x][y])add((i-1)*n+j,p,10000000),add(p,(i-1)*n+j,0);}int ans=Dinic();printf("%d",n*n-m-ans);
}