我想从字符串中删除所有标点符号并在C中将所有大写字母小写,任何建议?
Loop over the characters of the string. Whenever you meet a punctuation ( ispunct
), don't copy it to the output string. Whenever you meet an "alpha char" ( isalpha
), use tolower
to convert it to lowercase.
All the mentioned functions are defined in <ctype.h>
You can either do it in-place (by keeping separate write pointers and read pointers to the string), or create a new string from it. But this entirely depends on your application.
Just a sketch of an algorithm using functions provided by ctype.h
:
#include <ctype.h>
void remove_punct_and_make_lower_case(char *p)
{
char *src = p, *dst = p;
while (*src)
{
if (ispunct((unsigned char)*src))
{
/* Skip this character */
src++;
}
else if (isupper((unsigned char)*src))
{
/* Make it lowercase */
*dst++ = tolower((unsigned char)*src);
src++;
}
else if (src == dst)
{
/* Increment both pointers without copying */
src++;
dst++;
}
else
{
/* Copy character */
*dst++ = *src++;
}
}
*dst = 0;
}
Standard caveats apply: Completely untested; refinements and optimizations left as exercise to the reader.
The idiomatic way to do this in C is to have two pointers, a source and a destination, and to process each character individually: eg
#include <ctype.h>
void reformat_string(char *src, char *dst) {
for (; *src; ++src)
if (!ispunct((unsigned char) *src))
*dst++ = tolower((unsigned char) *src);
*dst = 0;
}
src and dst can be the same string since the destination will never be larger than the source.
Although it's tempting, avoid calling tolower(*src++)
since tolower may be implemented as a macro.
Avoid solutions that search for characters to replace (using strchr or similar), they will turn a linear algorithm into a geometric one.
Here's a rough cut of an answer for you:
void strip_punct(char * str) {
int i = 0;
int p = 0;
int len = strlen(str);
for (i = 0; i < len; i++) {
if (! ispunct(str[i]) {
str[p] = tolower(str[i]);
p++;
}
}
}
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