C Caesar Chiper - 大键错误

Question

我在网上搜索了很长时间，寻找 C 语言的简单凯撒 chiper/encryption 算法。我找到了一个，但并不完美，所以我已经更改了代码。仍然有问题，因为一位朋友说该程序也应该能够处理大密钥。例如 text "Hello World" with a Key: 50... 如果我这样做，我会得到以下信息：（控制台输出）

This tiny application encodes plain text to the Caesar Encryption
Type in some text to decode: Hello World
Type in the key/shifting of the letters:
50
`}ääç oçèä|

哪里错了....也许问题出在 char/array - 我不知道...所以如果你能帮助我，我会很高兴:)

这里是源代码（有一些注释）：

#include <stdio.h>
#include <conio.h>
#include <wchar.h>

int main()
{
unsigned char array[100], shifting; //creating 2 arrays for the encryption
//I changed it to unsigned char because otherwise Z with key 6/7 dosen't work
int z; //This is our key
printf("This tiny application encodes plain text to the Caesar Encryption\n");

printf("Type in some text to decode :");
fgets(array, 100, stdin); //because gets() is bad I'am using fgets()
printf("Type in the key/shifting of the letters:\n");
scanf("%d", &z);

for (int i = 0; array[i] != '[=11=]'; i++) 
{
    shifting = array[i]; //overgive values from array to shifting
    if (shifting >= 'a' && shifting <= 'z') { //check the containing lowercase letters
        shifting = shifting + z;

        if (shifting > 'z') {
            shifting = shifting - 'z' + 'a' - 1; // if go outside the ascii alphabeth this will be done
        }

        array[i] = shifting;
    }
    else if (shifting >= 'A' && shifting <= 'Z') { //the same for uppercase letters
        shifting = shifting + z;

        if (shifting > 'Z') {
            shifting = shifting - 'Z' + 'A' - 1;
        }

        array[i] = shifting;
    }
}

printf("%s\n", array);

return 0;
}

Answer 1

您的问题根源在这里：

    if (shifting > 'z') {
        shifting = shifting - 'z' + 'a' - 1; // if go outside the ascii alphabeth this will be done
    }

英文字母的长度是多少？现在是 26.

如果您给 z 大于 26，则按字母长度单次递减是不够的。您应该确保 z 不超过字母表的长度，或者重复递减直到结果符合字母表范围。

解决方案 1：

    int asciiAlphabetLength = 'z' - 'a' + 1;

    printf("Type in the key/shifting of the letters:\n");
    scanf("%d", &z);
    z %= asciiAlphabetLength;

解决方案 2：

    shifting += z;

    while (shifting > 'z') {
        shifting -= asciiAlphabetLength; // while outside the ascii alphabeth reduce
    }

C Caesar Chiper - 大键错误

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