CSP2022-jT4 k=0部分做法,死活搞不出来

#include <bits/stdc++.h>
#define rep(i,l,r) for(int i=l;i<=r;++i)

using namespace std;

struct Point
{
    int x,y;
    bool operator<(const Point &_a){if(x!=_a.x)return x<_a.x;return y<_a.y;}
};

int n,k;
Point a[523];
int dp[523];

signed main()
{
    cin>>n>>k;
    rep(i,1,n)
        cin>>a[i].x>>a[i].y;
    sort(a+1,a+1+n);
    rep(i,1,n)
        dp[i]=1;
    rep(i,2,n)
        rep(j,1,i-1)
            if((a[i].x-a[j].x==1&&a[i].y==a[j].y)||(a[i].y-a[j].y==1&&a[i].x==a[j].x))
            {
                dp[i]=max(dp[i],dp[j]+1);
                // cout<<dp[i]<<endl;
            }
    // rep(i,1,n)
    //     cout<<dp[i]<<endl;
    cout<<dp[n];
}

球球你们了...