Question

How to implement the memchr function in C

Answer 1

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

void* memchr(const void* s, int c, size_t n) {
	// find first occurrence of c in s from s[0] to s[n]
	const unsigned char ch = c;
	const unsigned char* p = (const unsigned char*)s;

	for (; 0 < n; p++, n--)
		if (*p == ch)
			return (void*)p;
	return NULL;
}

int main()
{
	char str[32] = "c programming";

	puts(memchr(str, 'm', strlen(str)));

	return 0;
}





/*
run:
         
mming
      
*/

 

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Answer 2

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

void* memchr(const void* s, int c, size_t n) {
	// find first occurrence of c in s from s[0] to s[n]
	const unsigned char ch = c;
	const unsigned char* p = (const unsigned char*)s;

	for (; 0 < n; p++, n--)
		if (*p == ch)
			return (void*)p;
	return NULL;
}

int main()
{
	char str[32] = "c programming";

	char* p = memchr(str, 'm', 5);

	if (p != NULL)
		puts(p);
	else
		puts("Not Found");

	return 0;
}





/*
run:
         
Not Found
      
*/

 

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