题解 | #字符串加解密#

#include <stdio.h>

#define DIFF_VALUE ('a'-'A')

static int encrypt_print(char *encrypt, int n)
{
    if(!encrypt)
    {
        return -1;
    }
    for(int i = 0; i < n; i++)
    {
        if(encrypt[i] >= 'A' && encrypt[i] <= 'Z')
        {
            if(encrypt[i] == 'Z')
            {
                encrypt[i] = 'a';
            }
            else
            {
                encrypt[i] += (1 + DIFF_VALUE);
            }
        }
        else if(encrypt[i] >= 'a' && encrypt[i] <= 'z')
        {
            if(encrypt[i] == 'z')
            {
                encrypt[i] = 'A';
            }
            else
            {
                encrypt[i] += (1 - DIFF_VALUE);
            }
        }
        else if(encrypt[i] >= '0' && encrypt[i] <= '9')
        {
            if(encrypt[i] == '9')
            {
                encrypt[i] = '0';
            }
            else
            {
                encrypt[i]++;
            }
        }
    }
    printf("%s\n", encrypt);
    return 0;
}

static int decode_print(char *decode, int n)
{
    if(!decode)
    {
        return -1;
    }
    for(int i = 0; i < n; i++)
    {
        if(decode[i] >= 'A' && decode[i] <= 'Z')
        {
            if(decode[i] == 'A')
            {
                decode[i] = 'z';
            }
            else
            {
                decode[i] += (-1 + DIFF_VALUE);
            }
        }
        else if(decode[i] >= 'a' && decode[i] <= 'z')
        {
            if(decode[i] == 'a')
            {
                decode[i] = 'Z';
            }
            else
            {
                decode[i] -= (1 + DIFF_VALUE);
            }
        }
        else if(decode[i] >= '0' && decode[i] <= '9')
        {
            if(decode[i] == '0')
            {
                decode[i] = '9';
            }
            else
            {
                decode[i]--;
            }
        }
    }
    printf("%s\n", decode);
    return 0;
}

int main()
{
    char encrypt[1000] = {0};
    char decode[1000] = {0};
    gets(encrypt);
    gets(decode);
    int len1 = strlen(encrypt);
    int len2 = strlen(decode);
    encrypt_print(encrypt, len1);
    decode_print(decode, len2);
    return 0;
}