DNA （C语言代码）

解题思路以及注意事项：

代码比较长，大家可以静下心来直接看代码，有详细注释                    x         x

小图形的样子由a决定，比如a=3，则小图形的样子是x x     a=5就是      x  x

                                                                                x                            x

                                  共占三行                                x x                        x  x      共五行

                                                                                                         x         x

如果是第奇数个小图形，完全输出，偶数就得截去最上面和最下面的

实例代码：

    #include<stdio.h>  
    int main()  
    {  
        int t;  //t表示有几组数据
        int a,b;  //a,b分别是样子和重复次数
        int i,j,k;  //都是用来循环的
        scanf("%d",&t);  //给t赋值
        while(t--)  
        {  
            scanf("%d%d",&a,&b);  
            for(i=1;i<=b;i++)  
            {  
                if(i%2==1)                                  
//当是第奇数个小图形的时候，就将小图形完全输出   
                {  
                    for(j=1;j<=a;j++)  
                    {  
                        for(k=1;k<=a;k++)  
                        {  
                            if(k==j||k==a-j+1)  
                                printf("X");  
                            else  
                                printf(" ");  
                            if((j<=a/2&&k==a-j+1)||(j>a/2&&k==j))  
                                break;                                    
//跳出循环，避免输出多余的空格   
                        }  
                        printf("\n");  
                    }  
                }  
                else  
                {                          
                    for(j=2;j<=a-1;j++)
                    {        
//当是第偶数个小图形的时候，将小图形首尾各截去一行再输出               
                        for(k=1;k<=a;k++)  
                        {  
                            if(k==j||k==a-j+1)  
                                printf("X");  
                            else  
                                printf(" ");  
                            if((j<=a/2&&k==a-j+1)||(j>a/2&&k==j))  
                                break;  
                        }  
                        printf("\n");  
                    }  
                }  
            }  
            if(b%2==0)   
//如果一共有偶数个小图形，那么在最后就需要再加一个尾，即小图形的最后一行   
            {  
                for(i=1;i<=a;i++)  
                {  
                    if(i==1||i==a)  
                        printf("X");  
                    else  
                        printf(" ");  
                }  
                printf("\n");  
            }  
            if(t!=0)  
                printf("\n");  
        }  
        return 0;  
    }

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