使用了匈牙利捏

#include<bits/stdc++.h>
using namespace std;
/* --------------- fast io --------------- */ // begin
namespace Fread {
const int SIZE = 1 << 21;
char buf[SIZE], *S, *T;
inline char getchar() {
    if (S == T) {
        T = (S = buf) + fread(buf, 1, SIZE, stdin);
        if (S == T) return '\n';
    }
    return *S++;
}
} // namespace Fread
namespace Fwrite {
const int SIZE = 1 << 21;
char buf[SIZE], *S = buf, *T = buf + SIZE;
inline void flush() {
    fwrite(buf, 1, S - buf, stdout);
    S = buf;
}
inline void putchar(char c) {
    *S++ = c;
    if (S == T) flush();
}
struct NTR {
    ~ NTR() { flush(); }
} ztr;
} // namespace Fwrite
#ifdef ONLINE_JUDGE
#define getchar Fread :: getchar
#define putchar Fwrite :: putchar
#endif
namespace Fastio {
struct Reader {
    template<typename T>
    Reader& operator >> (T& x) {
        char c = getchar();
        T f = 1;
        while (c < '0' || c > '9') {
            if (c == '-') f = -1;
            c = getchar();
        }
        x = 0;
        while (c >= '0' && c <= '9') {
            x = x * 10 + (c - '0');
            c = getchar();
        }
        x *= f;
        return *this;
    }
    Reader& operator >> (char& c) {
        c = getchar();
        while (c == ' ' || c == '\n') c = getchar();
        return *this;
    }
    Reader& operator >> (char* str) {
        int len = 0;
        char c = getchar();
        while (c == ' ' || c == '\n') c = getchar();
        while (c != ' ' && c != '\n' && c != '\r') { // \r\n in windows
            str[len++] = c;
            c = getchar();
        }
        str[len] = '\0';
        return *this;
    }
    Reader(){}
} cin;
const char endl = '\n';
struct Writer {
    template<typename T>
    Writer& operator << (T x) {
        if (x == 0) { putchar('0'); return *this; }
        if (x < 0) { putchar('-'); x = -x; }
        static int sta[45];
        int top = 0;
        while (x) { sta[++top] = x % 10; x /= 10; }
        while (top) { putchar(sta[top] + '0'); --top; }
        return *this;
    }
    Writer& operator << (char c) {
        putchar(c);
        return *this;
    }
    Writer& operator << (char* str) {
        int cur = 0;
        while (str[cur]) putchar(str[cur++]);
        return *this;
    }
    Writer& operator << (const char* str) {
        int cur = 0;
        while (str[cur]) putchar(str[cur++]);
        return *this;
    }
    Writer(){}
} cout;
} // namespace Fastio
#define cin Fastio :: cin
#define cout Fastio :: cout
#define endl Fastio :: endl
/* --------------- fast io --------------- */ // end
int za[205][205],npy[40005],vis[40005];
int zk(int x,int y,int n)
{
	return (x-1)*n+y;
}
vector<int> g[40005];
const int dx[]={1,1,2,2,-1,-1,-2,-2};
const int dy[]={2,-2,1,-1,2,-2,1,-1};
int dfs(int u,int rt)
{
	if(vis[u]==rt)return 0;
	vis[u]=rt;
	for(int v:g[u])
	{
		if(!npy[v]||dfs(npy[v],rt))
		{
			npy[v]=u;
			return 1;
		}
	}
	return 0;
}
int main()
{
	int n,m;
	cin>>n>>m;
	for(int i=1;i<=m;i++)
	{
		int x,y;
		cin>>x>>y;
		za[x][y]=1;
	}
	for(int i=1;i<=n;i++)
	{
		for(int j=1;j<=n;j++)
		{
			if(za[i][j])continue;
			for(int k=0;k<8;k++)
			{
				int a=i+dx[k],b=j+dy[k];
				if(a<1||a>n||b<1||b>n)continue;
				if(za[a][b])continue;
				if((i+j)%2)g[zk(i,j,n)].push_back(zk(a,b,n));
				else       g[zk(a,b,n)].push_back(zk(i,j,n));//here
			}
		}
	}
	int ans=n*n-m;
	for(int i=1;i<=n;i++)for(int j=1;j<=n;j++)if((i+j)%2)ans-=dfs(zk(i,j,n),zk(i,j,n));
	cout<<ans;
	return 0;
}

如上代码TLE最后一个点，但把标here的那一行去掉就过了，而且跑得飞快（63ms）

怎么回事啊