codeforce 980B - Marlin 思维|构造

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Scanner;


public class Main{
    

    static char a[][] = new char[105][105];
    public static void main(String[] args){
        Scanner sc = new Scanner(new BufferedInputStream(System.in));
        PrintWriter pw = new PrintWriter(new BufferedOutputStream(System.out));
        
        int n,k;
        n = sc.nextInt();
        k = sc.nextInt();
        int nowrow=2,le=2,ri=n-1,time = n-2;
        int cnt=0;
        
        if(k%time==1||(k<time&&k%2==1)){
            a[3][n/2+1] = '#';
            k--;
        }//需要注意如果是奇数 表示的是相对于行可放的数量是奇数
        
        while(k>0){
            k--;
            if(ri<le){
                nowrow++;
                le=2;
                ri = n-1;
            }
            if(cnt%2!=0) a[nowrow][ri--] = '#';
            else a[nowrow][le++] = '#';
            cnt++;
        }
        pw.println("YES");
        for(int i=1;i<=4;i++){
            for(int j=1;j<=n;j++)
            if(a[i][j]=='#') pw.print(a[i][j]);
            else pw.print('.');
            pw.println();
        }
        pw.flush();
    }
}import java.io.BufferedInputStream;
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