打印矩形框

#include<stdio.h>
#include <string>
#include<math.h>
#include<iostream>
using namespace std;
char res[205][205];
int main()
{
	int n;
	scanf("%d",&n);
	int sum = 3*n+(n-1);

	for(int i=0;i<sum/2+1;i++){
        char a='*';
        char b = '_';
        if(i%2==1){
            a='_';
            b = '*';
        }
        if(i==sum/2){
            for(int j=0;j<sum;j++){
            if(j%2==0){
               res[i][j]='*';
            }else{
               res[i][j]='-';
            }
        }
            break;
        }
        for(int j=0;j<i;j++){
            if(j%2==0){
               res[i][j]='*';
            }else{
               res[i][j]='-';
            }
        }
        for(int j=i;j<sum-i;j++){
            res[i][j]=a;
        }
        for(int j=sum-i;j<sum;j++){
            if((j-sum+i)%2==0){
               res[i][j]=b;
            }else{
               res[i][j]=a;
            }
        }
	}
	int ii=1;
    for(int k=0;k<sum;k++){
       if(k>(sum/2)){
        cout<<res[k-ii*2]<<endl;
        ii++;
       }else{
         cout<<res[k]<<endl;
       }
    }
    return 0;
}