使用 strdup（）是一种方法，但是如果您可以修改 text 本身，则有一个更好的选择。您可以简单地使用：
void encrypt(char *text, int k) {
while (*text) {
// Identify if the value is an alphabet
if (isalpha(*text) != 0) {
if (isupper(*text) != 0) {
// Apply formula to uppercase character
*text = ((*text - 'A' + k) % 26) + 'A';
} else {
// Apply formula to lowercase character
*text = ((*text - 'a' + k) % 26) + 'a';
}
}
text++;
}
}
一些解释： while（*text）表示以下内容，直到存储 at text是0。 text ++; 增加指针。因此，在该行之后，文本指向下一个字符。所有的操作只是（int i = 0; text [i]！='\ 0'; i ++）的另一种做法，但不需要新变量。
As mentioned in the comments, you are writing to a NULL pointer since you set ciphertext to NULL. What you want to do is allocate memory for ciphertext. This can be done with char *ciphertext = strdup(text); which sets up ciphertext with a newly allocated pointer to a copy of the null-terminated char pointer named text. Using either this solution or the one below, you don't need to // Store non-alphabetical value as it is since that value is already there.
Using strdup() is one method, but there is a better option if you can modify text itself. You can simply use:
void encrypt(char *text, int k) {
while (*text) {
// Identify if the value is an alphabet
if (isalpha(*text) != 0) {
if (isupper(*text) != 0) {
// Apply formula to uppercase character
*text = ((*text - 'A' + k) % 26) + 'A';
} else {
// Apply formula to lowercase character
*text = ((*text - 'a' + k) % 26) + 'a';
}
}
text++;
}
}
A little explanation: while (*text) means do the following until the value stored at text is 0. text++; increments the pointer. So after that line text is pointing to the next char. All that does is just another way of doing for (int i = 0; text[i] != '\0'; i++) but without needing a new variable.
Note that the above code no longer returns the result of the "encryption". Rather, it modifies the content of the char * you passed it. No memory allocation necessary-- the caller did it for you.
If you opt to use the above code, you'll need to do something like this to print the result:
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如注释中所述，您正在将其写入零指针，因为您将
ciphertext设置为null。您要做的是为ciphertext分配内存。这可以使用char *ciphertext = strdup（text）;设置ciphertext，并带有新分配的指针，可用于null终止的char指数文本。使用此解决方案或下面的解决方案，您不需要//存储非按字母的值，因为它已经存在，因为该值已经存在。使用
strdup（）是一种方法，但是如果您可以修改text本身，则有一个更好的选择。您可以简单地使用：一些解释：
while（*text）表示以下内容，直到存储 at text是0。text ++;增加指针。因此，在该行之后，文本指向下一个字符。所有的操作只是（int i = 0; text [i]！='\ 0'; i ++）的另一种做法，但不需要新变量。请注意，以上代码不再返回“加密”的结果。相反，它修改了您传递的
char *的内容。无需内存分配 - 呼叫者为您做到了。如果您选择使用上述代码，则需要执行类似的操作来打印结果：
As mentioned in the comments, you are writing to a NULL pointer since you set
ciphertextto NULL. What you want to do is allocate memory forciphertext. This can be done withchar *ciphertext = strdup(text);which sets upciphertextwith a newly allocated pointer to a copy of the null-terminated char pointer namedtext. Using either this solution or the one below, you don't need to// Store non-alphabetical value as it issince that value is already there.Using
strdup()is one method, but there is a better option if you can modifytextitself. You can simply use:A little explanation:
while (*text)means do the following until the value stored at text is 0.text++;increments the pointer. So after that linetextis pointing to the next char. All that does is just another way of doingfor (int i = 0; text[i] != '\0'; i++)but without needing a new variable.Note that the above code no longer returns the result of the "encryption". Rather, it modifies the content of the
char *you passed it. No memory allocation necessary-- the caller did it for you.If you opt to use the above code, you'll need to do something like this to print the result: