如何使用 'do while' 循环重复 'for' 循环

Question

这是我的 Vigenere 密码。我正在尝试使用 do while 循环对用户输入的键重复迭代。密钥应用于用户输入的明文单词，一次输入一个字母。我需要能够遍历密钥直到明文单词结束，以防密钥比单词短。我尝试使用 do-while 循环添加重复，第一个 for 循环是关键迭代。

'do while' 循环的最后一行抛出未声明标识符 i 的错误。这是我遇到的唯一错误。内部 'for' 循环来自凯撒密码并通过了所有检查。我认为我的 do while 循环是错误的。如果我添加 char* word[i] 或 word[i] 的定义，无论我把它放在哪里，我都会得到一个遮蔽错误。我想使用这段代码而不是完全改变它，所以我知道是否可以这样做。但是，我们欢迎任何建议。

int main(int argc, char* argv[])
{
    if (argc<2) //key
    {
        printf("Please enter your word key"); //prompts if no key is entered
        return 1;
    }

    char* key = (argv[1]);

    if(argc>=2)
    {
        printf("plaintext:");
        char* word = GetString();

        printf("ciphertext:");

        do
        {  //starts loop to repeat following for loop

            for(int l=0; l<strlen(key); l++) //iterate over letters in key
            {
                int num=l;
                for(int i=0; i<strlen(word); i++)  //iterates through word entered by user as plaintext
                {
                    if(isupper(word[i]))  //if original characters are uppercase
                    {
                        int cipher = (word[i] + num -65) % 26 + 65;
                        printf("%c", cipher);
                    }
                    else if(islower(word[i]))  //if original characters are lowercase
                    {
                        int cipher = (word[i] + num - 97) % 26 + 97;
                        printf("%c", (cipher));
                    }
                    else    //all other types of characters
                    {
                        printf("%c", word[i]);
                    }
                }
            }
            printf("\n");
        }while((word[i])<strlen(word));  // loop to recommence iterating over letters in the key   (i throwing undeclared identifier error)
    }
}

Answer 1

我认为你的循环 [levels] 太多了。

如果密钥长度在单词完成之前用完，则从单词的开头重新开始加密单词（即错误）。

主要目的是遍历所有单词字符。递增 i 的单个循环有效，提供它也递增 l [模密钥长度].

这是一个清理过的版本[请原谅无偿的样式清理]：

#include <stdio.h>
#include <string.h>
#include <ctype.h>

// NOTE: I don't have GetString on my system
char *FakeGetString(void);

int
main(int argc, char *argv[])
{

    // key
    // prompts if no key is entered
    if (argc < 2) {
        printf("Please enter your word key");
        return 1;
    }

    char *key = (argv[1]);
    int klen = strlen(key);

    if (argc >= 2) {
        printf("plaintext:");

#if 0
        char *word = GetString();
#else
        char *word = FakeGetString();
#endif

        int wlen = strlen(word);

        printf("ciphertext:");

        // current key index
        int l = 0;

        // starts loop to repeat following for loop
        // iterates through word entered by user as plaintext
        // advance to next key char [with wrap to beginning if we're short]
        for (int i = 0;  i < wlen; ++i, l = (l + 1) % klen) {
            int num = key[l];
            int cipher;

            // if original characters are uppercase
            if (isupper(word[i])) {
                cipher = (word[i] + num - 65) % 26 + 65;
            }

            // if original characters are lowercase
            else if (islower(word[i])) {
                cipher = (word[i] + num - 97) % 26 + 97;
            }

            // all other types of characters
            else {
                cipher = word[i];
            }

            printf("%c", cipher);
        }

        printf("\n");
    }

    return 0;
}

// NOTE: I don't have GetString on my system
char *
FakeGetString(void)
{
    static char buf[1000];
    char *cp;

    fgets(buf,sizeof(buf),stdin);
    cp = strchr(buf,'\n');
    if (cp != NULL)
        *cp = 0;

    return buf;
}

更新：

我写的上面的代码非常接近，但不是 Vigenere，因为你原来的方程式不对。键值必须是 offset/row 数字，因此需要从中减去 'A'（即关键字只能是大写）。

所以，这是更正后的版本[有一些额外的清理]：

#include <stdio.h>
#include <string.h>
#include <ctype.h>

// NOTE: I don't have GetString on my system
char *FakeGetString(void);

int
baseof(int chr)
{
    int base;

    // if original character is uppercase
    if (isupper(chr)) {
        base = 'A';
    }

    // if original character is lowercase
    else if (islower(chr)) {
        base = 'a';
    }

    // anything else
    else
        base = 0;

    return base;
}

int
main(int argc, char *argv[])
{
    int kval;
    int base;
    int i;

    // key
    // prompts if no key is entered
    if (argc < 2) {
        printf("Please enter your word key\n");
        return 1;
    }

    char *key = argv[1];
    int klen = strlen(key);

    // key must be uppercase and we only want row numbers
    for (i = 0;  i < klen;  ++i) {
        kval = key[i];
        base = baseof(kval);

        if (base) {
            key[i] = kval - base;
            continue;
        }

        printf("Key value must be only A-Z\n");
        return 1;
    }

    if (argc >= 2) {
        printf("plaintext:");

#if 0
        char *word = GetString();
#else
        char *word = FakeGetString();
#endif
        int wlen = strlen(word);

        printf("ciphertext:");

        // starts loop to repeat following for loop
        // iterates through word entered by user as plaintext
        // advance to next key char [with wrap to beginning if we're short]
        for (i = 0;  i < wlen;  ++i) {
            int wval = word[i];
            int cipher;

            base = baseof(wval);

            // uppercase or lowercase
            if (base) {
                kval = key[i % klen];
                cipher = ((wval - base) + kval) % 26 + base;
            }

            // all other types of characters
            else {
                cipher = wval;
            }

            printf("%c",cipher);
        }

        printf("\n");
    }

    return 0;
}

// NOTE: I don't have GetString on my system
char *
FakeGetString(void)
{
    static char buf[1000];
    char *cp;

    fgets(buf,sizeof(buf),stdin);
    cp = strchr(buf,'\n');
    if (cp != NULL)
        *cp = 0;

    return buf;
}

更新#2：

Your code passed all check50 checks except this one: :( encrypts "world, say hello!" as "xoqmd, rby gflkp!" using "baz" as keyword \ expected output, but not "ciphertext:xoqmd, szz gflkp!\n". It didn't encipher just the word 'say' properly, which is weird.

我使用 Vigenere 维基百科页面上的测试 data/example 对其进行了测试，但它只有一个现成的测试示例 [没有空格或标点符号]。

This was the only check which contained a space (before the word 'say'). The spaces have to be directly copied. Perhaps that's why.

空格是直接复制过来的，这样就可以了。但是...

正确的方法是，当复制非字母字符时，键索引必须而不是递增。

我的版本使用 i 索引短语，使用 i % klen 索引键，因此键索引总是 [有效] 递增。这就是错误。

讽刺的是，我也曾想过这个问题，但当时没有扩展的测试数据

因此，解决方案是将索引变量分开[再次:-)]。

这是更正后的版本。当我修复它时，我将 i 变量重命名为更具描述性的内容（例如 widx）并（重新）创建了键的索引变量（例如 kidx）。

请注意，现在 kidx 仅在实际加密字符时递增。 "pass through" 案例不是

#include <stdio.h>
#include <string.h>
#include <ctype.h>

// NOTE: I don't have GetString on my system
char *FakeGetString(void);

int
baseof(int chr)
{
    int base;

    // if original character is uppercase
    if (isupper(chr)) {
        base = 'A';
    }

    // if original character is lowercase
    else if (islower(chr)) {
        base = 'a';
    }

    // anything else
    else
        base = 0;

    return base;
}

int
main(int argc, char *argv[])
{
    int kval;
    int base;
    int widx;
    int kidx;

    // key
    // prompts if no key is entered
    if (argc < 2) {
        printf("Please enter your word key\n");
        return 1;
    }

    char *key = argv[1];
    int klen = strlen(key);

    // key must be uppercase and we only want row numbers
    for (kidx = 0;  kidx < klen;  ++kidx) {
        kval = key[kidx];
        base = baseof(kval);

        if (base) {
            key[kidx] = kval - base;
            continue;
        }

        printf("Key value must be only A-Z\n");
        return 1;
    }

    if (argc < 2)
        return 1;

    printf("plaintext:");

#if 0
    char *word = GetString();
#else
    char *word = FakeGetString();
#endif
    int wlen = strlen(word);

    printf("ciphertext:");

    kidx = 0;

    // starts loop to repeat following for loop
    // iterates through word entered by user as plaintext
    // advance to next key char [with wrap to beginning if we're short]
    for (widx = 0;  widx < wlen;  ++widx) {
        int wval = word[widx];
        int cipher;

        base = baseof(wval);

        // uppercase or lowercase
        if (base) {
            kval = key[kidx];
            cipher = ((wval - base) + kval) % 26 + base;
            kidx = (kidx + 1) % klen;
        }

        // all other types of characters
        else {
            cipher = wval;
        }

        printf("%c",cipher);
    }

    printf("\n");

    return 0;
}

// NOTE: I don't have GetString on my system
char *
FakeGetString(void)
{
    static char buf[1000];
    char *cp;

    fgets(buf,sizeof(buf),stdin);
    cp = strchr(buf,'\n');
    if (cp != NULL)
        *cp = 0;

    return buf;
}

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