String matching: Difference between revisions

Code without using string library to demonstrate how char strings are just pointers:

<lang C>#include <stdio.h>

/* returns 0 if no match, 1 if matched, -1 if matched and at end */

int s_cmp(char *a, char *b)

{

char c1 = 0, c2 = 0;

while (c1 == c2) {

c1 = *(a++);

if ('\0' == (c2 = *(b++)))

return c1 == '\0' ? -1 : 1;

}

return 0;

}

/* returns times matched */

int s_match(char *a, char *b)

{

int i = 0, count = 0;

printf("matching `%s' with `%s':\n", a, b);

while (a[i] != '\0') {

switch (s_cmp(a + i, b)) {

case -1:

printf("matched: pos %d (at end)\n\n", i);

return ++count;

case 1:

printf("matched: pos %d\n", i);

break;

}

i++;

}

printf("end match\n\n");

return count;

}

int main()

{

s_match("A Short String", "ort S");

s_match("aBaBaBaBa", "aBa");

s_match("something random", "Rand");

return 0;

}</lang>

Output:<pre>matching `A Short String' with `ort S':

matched: pos 4

end match

matching `aBaBaBaBa' with `aBa':

matched: pos 0

matched: pos 2

matched: pos 4

matched: pos 6 (at end)

matching `something random' with `Rand':

end match</pre>