題目

https://www.luogu.org/problemnew/show/P3355#sub

解題思路

這道題自從上一次得了90分後，就一直擱置了很久，找不到錯誤。請各位大佬幫忙！！！

程式碼匈牙利演算法

#include<cstdio>
#include<cstring>
#include<string>
using namespace std;
const int b[8]={-2,-1,1,2,2,1,-1,-2},c[8]={1,2,2,1,-1,-2,-2,-1};
struct node{int y,next;
 
}a[320032]; 
int rr,ans,sum,add,n,m,xx,yy,link[40001],v[40001],list[40001],t[201][201];
inline int read()
{
    int f=0; char c=getchar(); 
    while(!isdigit(c)) c=getchar(); 
    while(isdigit(c)) f=(f<<3)+(f<<1)+c-48,c=getchar();
    return f;
}
void write(int x){if (x>9) write(x/10); putchar(x%10+
 
48);}
inline bool find (int q){
    for (register int i=list[q];i;i=a[i].next)
      if (!v[a[i].y])
      {
            v[a[i].y]=1; 
            int u=link[a[i].y]; 
            link[a[i].y]=q; 
            if (!u||find(u)) return 1; 
            link[a[i].y]=u; 
      }	
    return 0;
}
signed main
 
()
{
    n=read(); m=read();  ans=n*n-m; 
    for (register int i=1;i<=m;i++) t[(xx=read())][(yy=read())]=-1; 
    for (register int i=1;i<=n;i++)
     for (register int j=1;j<=n;j++)
     if (!t[i][j]&&((i+j)&1))
     {
     	t[i][j]=++add;
     	for (register int k=0;k<8;k++)
         {
     	   xx=i+b[k]; yy=j+c[k];
           if ((xx>=1&&xx<=n)&&(yy>=1&&yy<=n))
           {
           	 if (!t[xx][yy]) t[xx][yy]=++rr; 
           	 if (t[xx][yy]!=-1) 
			   a[++sum].y=t[xx][yy],a[sum].next=list[add],list[add]=sum; 
           }
     	}
     }
   for (register int i=1;i<=add;i++)
   {
   	    memset(v,0,sizeof(v));
   	    if (find(i)) ans--; 
   }
   write(ans); 
   return 0; 
}