题解 | #字符串加解密#

#include <stdio.h>

char getEnChar(char ch)
{
    char ret = 0;
    if(ch >= 'a' && ch <= 'z')
    {
        ret = (ch + 1 - 'a') % 26 + 'A';
    }
    else if(ch >= 'A' && ch <= 'Z')
    {
        ret = (ch + 1 - 'A') % 26 + 'a';
    }
    else if(ch >= '0' && ch <= '9')
    {
        ret = (ch + 1 - '0') % 10 + '0';
    }
    return ret;
}

char getDeChar(char ch)
{
    char ret = 0;
    if(ch >= 'a' && ch <= 'z')
    {
        ret = (ch + 25 - 'a') % 26 + 'A';
    }
    else if(ch >= 'A' && ch <= 'Z')
    {
        ret = (ch + 25 - 'A') % 26 + 'a';
    }
    else if(ch >= '0' && ch <= '9')
    {
        ret = (ch + 9 - '0') % 10 + '0';
    }
    return ret;
}
int main() {
    char ch = 0;
    char flag = 0;
    while(EOF != (ch = getchar()))
    {
        if(ch == '\n')
        {
            flag = 1;
            printf("\n");
            continue;
        }else{
            if(0 == flag)
            {
                printf("%c",getEnChar(ch));
            }else if(1 == flag)
            {
                printf("%c",getDeChar(ch));
            }
        }
    }
    return 0;
}