Strip a set of characters from a string: Difference between revisions

===With table lookup===

<lang C>#include <stdio.h>

#include <stdlib.h>

#include <string.h>

char *strip(char * str, char *pat)

{

/* char replacement is typically done with lookup tables if

* the replacement set can be large: it turns O(m n) into

* O(m + n).

* If same replacement pattern is going to be applied to many

* strings, it's better to build a table beforehand and reuse it.

* If charset is big like unicode, table needs to be implemented

* more efficiently, say using bit field or hash table -- it

* all depends on the application.

*/

int i = 0, tbl[128] = {0};

while (*pat != '\0') tbl[(int)*(pat++)] = 1;

char *ret = malloc(strlen(str));

do {

if (!tbl[(int)*str])

ret[i++] = *str;

} while (*(str++) != '\0');

/* assuming realloc is efficient and succeeds; if not, we could

* do a two-pass, count first, alloc and strip second

*/

return realloc(ret, i);

}

int main()

{

char * x = strip("She was a soul stripper. She took my heart!", "aei");

printf(x);

free(x);

return 0;

}</lang>Output same as above.