编程实现凯撒密码

c语言编程实现凯撒密码

#include 
int main()
{
    char str[81];
    int i=0,offset;
    gets(str);
    scanf("%d",&offset);
    if(offset%26!=0||offset==0)
    {
        while(str[i]!='')
    {
        if(str[i]>='A'&&str[i]<='Z')
        {
            if(str[i]+offset>'Z')
            {
                str[i]='A'+offset-('Z'-str[i])-1;
            }
            else if(str[i]+offset<'A')
            {
                str[i]='Z'+offset+(str[i]-'A')+1;
            }
            else str[i]=str[i]+offset;
        }
        if(str[i]>='a'&&str[i]<='z')
        {
            if(str[i]+offset>'z')
            {
                str[i]='a'+offset-('z'-str[i])-1;
            }
            else if(str[i]+offset<'a')
            {
                str[i]='z'+offset+(str[i]-'a')+1;
            }
            else str[i]=str[i]+offset;
        }
        i++;
    }
    }
    if(offset%26==0&&offset!=0) puts(str);
    puts(str);
    return 0;
}