Question

我不确定我缺少用于pset2替换的代码。当我运行Check50时，它给出以下输出：

:) substitution.c exists
:) substitution.c compiles
:( encrypts "A" as "Z" using ZYXWVUTSRQPONMLKJIHGFEDCBA as key
    output not valid ASCII text
:( encrypts "a" as "z" using ZYXWVUTSRQPONMLKJIHGFEDCBA as key
    output not valid ASCII text
:( encrypts "ABC" as "NJQ" using NJQSUYBRXMOPFTHZVAWCGILKED as key
    output not valid ASCII text
:( encrypts "XyZ" as "KeD" using NJQSUYBRXMOPFTHZVAWCGILKED as key
    output not valid ASCII text
:) encrypts "This is CS50" as "Cbah ah KH50" using YUKFRNLBAVMWZTEOGXHCIPJSQD as key
:) encrypts "This is CS50" as "Cbah ah KH50" using yukfrnlbavmwzteogxhcipjsqd as key
:) encrypts "This is CS50" as "Cbah ah KH50" using YUKFRNLBAVMWZteogxhcipjsqd as key
:) encrypts all alphabetic characters using DWUSXNPQKEGCZFJBTLYROHIAVM as key
:) handles lack of key
:) handles invalid key length
:) handles invalid characters in key
:) handles duplicate characters in key
:) handles multiple duplicate characters in key

正如人们可以看到的那样，我的代码在大多数情况下都可以正常工作，但是对于某些我无法弄清的代码，却给出了无效的ASCII文本输出。

这是我的代码的样子

#include <cs50.h>
#include <stdio.h>
#include <string.h>
#include <ctype.h>


int main(int argc, string argv[])
{
    if (argc != 2)
    {
        printf("Usage: ./substitution key\n");
        return 1;
    }
    else
    {
        if (strlen(argv[1]) != 26)
        {
            printf("Key must contain 26 characters\n");
            return 1;
        }
        else if (strlen(argv[1]) == 26)
        {
            for(int i = 0; i <= strlen(argv[1]); i++)
            {
                if (isdigit(argv[1][i]))
                {
                    printf("Key must only contain alphabetic characters\n");
                    return 1;
                }
            }
            for(int l = 0; l <= strlen(argv[1]); l++)
            {
                for(int j = 0; j < l; j++)
                {
                    if(argv[1][j] == argv[1][l])
                    {
                        printf("Key must not contain repeated characters\n");
                        return 1;
                    }
                }
            }
        }
    }
    string key = argv[1];
    string uppers = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    string lowers = "abcdefghijklmnopqrstuvwxyz";
    char upper_key[26], lower_key[26];
    string text = get_string("Plain Text: ");
    char ciphertext[strlen(text)];
    for(int i = 0; i < 26; i++)
    {
        upper_key[i] = toupper(key[i]);
    }
    for(int i = 0; i < 26; i++)
    {
        lower_key[i] = tolower(key[i]);
    }
    for(int i = 0; i < strlen(text); i++)
    {
        if(isupper(text[i]))
        {
            for(int j = 0; j < 26; j++)
            {
                if (text[i] == uppers[j])
                {
                    ciphertext[i] = upper_key[j];
                }
            }
        }
        else if(islower(text[i]))
        {
            for(int j = 0; j < 26; j++)
            {
                if(text[i] == lowers[j])
                {
                    ciphertext[i] = lower_key[j];
                }
            }
        }
        else
        {
            ciphertext[i] = text[i];
        }
    }
    printf("ciphertext: %s\n", ciphertext);
}

我对编码还很陌生，任何帮助将不胜感激...

Answer 1

我也遇到了同样的问题 '\0' 在密文末尾。

编辑：这是代码：

cypher_text[plain_txt_len] = '\0';

Answer 2

由于没有终止Eugene指出的密文，因此您的代码是从密文外部读取的。以下是内存访问错误，这里是link，用于将来重现/调试任何段错误。

Plain Text:
  Memory access error: reading from the outside of a memory space; abort execution.
  # Reading 1 bytes from 0xffd04071 will read undefined values.
  #
  # The memory-space-to-be-read (start:0xffd0406c, size:5 bytes) is bound to 'ciphertext' at
  #    file:/substitution.c::49, 10
  #
  #  0xffd0406c               0xffd04070
  #  +------------------------------+
  #  | the memory-space-to-be-read  |......
  #  +------------------------------+
  #                                  ^~~~~~~~~~
  #        the read starts at 0xffd04071 that is right after the memory-space end.
  #
  # Stack trace (most recent call first) of the read.
  # [0]  file:/musl-1.1.10/src/string/memchr.c::25, 9
  # [1]  file:/musl-1.1.10/src/stdio/vfprintf.c::602, 8
  # [2]  file:/musl-1.1.10/src/stdio/vfprintf.c::678, 8
  # [3]  file:/musl-1.1.10/src/stdio/printf.c::13, 8
  # [4]  file:/substitution.c::85, 5
  # [5]  [libc-start-main]

CS50-pset2-替代输出无效的ASCII文本

2 个答案: