求指点。凯撒密码，提交pta显示部分正确，自己输入很多数据测试都正确，找不到bug。

#include<stdio.h>
#include<math.h>
int main()
{    
    int offset;

    char a[81];
    char min[26]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
    char max[26]={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
    int i,k,m;
    gets(a);
    scanf("%d",&offset);
    for(i=0;a[i]!='\0';i++)
        {
        if(a[i]>='a' && a[i]<='z')
        {
            k=a[i]-'a';
            if(k<=(-offset)){
                m=(int)fabs(k+offset)%26;
                a[i]=min[26-m];
            }else{
                m=(k+offset)%26;
                a[i]=min[m];
            }
        }    
        else if(a[i]>='A' && a[i]<='Z')
        {
            k=a[i]-'A';
            if(k<=(-offset)){
                m=(int)fabs(k+offset)%26;
                a[i]=max[26-m];
            }else{
                m=(k+offset)%26;
                a[i]=max[m];
            }
        }        
    }        
    puts(a);
    return 0;
 } 

你的for循环左半拉大括号都没有。。。。。。