#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
/*
copy_if: Copies elements from src[] to dst[] only if they satisfy a predicate.
Parameters:
src - input array
n - number of elements in src
dst - output array (must be allocated by caller)
predicate- function pointer returning true for elements to be copied
Returns:
The number of elements copied into dst.
*/
size_t copy_if(const int *src, size_t n, int *dst, bool (*predicate)(int)) {
size_t count = 0;
for (size_t i = 0; i < n; i++) {
// If the predicate is satisfied, copy the element
if (predicate(src[i])) {
dst[count++] = src[i];
}
}
return count;
}
/*
Predicate:
Returns true if the number is even.
*/
bool is_even(int x) {
return (x % 2) == 0;
}
/*
Predicate:
Returns true if the number is greater than 10.
*/
bool greater_than_10(int x) {
return x > 10;
}
int main(void) {
// Input array
int src[] = {1, 2, 3, 4, 10, 11, 12, 20, 21};
size_t n = sizeof(src) / sizeof(src[0]);
// Allocate destination array (same size as src is safe)
int *dst = malloc(n * sizeof(int));
if (!dst) {
fprintf(stderr, "Memory allocation failed\n");
return 1;
}
// Use copy_if with the "is_even" predicate
size_t copied_even = copy_if(src, n, dst, is_even);
printf("Copying even numbers:\n");
for (size_t i = 0; i < copied_even; i++) {
printf("%d ", dst[i]);
}
printf("\n\n");
// Use copy_if with the "greater_than_10" predicate
size_t copied_gt10 = copy_if(src, n, dst, greater_than_10);
printf("Copying numbers > 10:\n");
for (size_t i = 0; i < copied_gt10; i++) {
printf("%d ", dst[i]);
}
printf("\n");
free(dst);
return 0;
}
/*
run:
Copying even numbers:
2 4 10 12 20
Copying numbers > 10:
11 12 20 21
*/
