Activity - Intersection of counters

1. Review set_iterate2. It shows how to construct the union of two sets.

2. Discuss how you would construct the intersection of two counters lists - for a counters node with a key that does not exist in both sets, we set its count to 0 in the intersection result.

3. Copy the skeleton code intersect to your cs50/ directory after logging to the plank server:

   $ cp -r /thayerfs/courses/22spring/cosc050/workspace/intersect/ .
   

   Here counters_intersect.c creates two dummy counters lists. We would like to complete the counters_intersect() function to perform counters intersection.

4. Once done, you can compile and run the code as below:

   $ mygcc -o intersect counters_intersect.c libcs50/libcs50-given.a 
   $ ./intersect 
   {3=2, 4=0, 5=1, 7=3, }
   

Hint: Make sure the counters_iterate() function. Below is a reminder on how counters_iterate() was implemented:

/**************** counters_iterate() ****************/
void
counters_iterate(counters_t *ctrs, void *arg,
		 void (*itemfunc)(void *arg, const int key, int count))
{
	if (ctrs != NULL && itemfunc != NULL) {
		// scan the counters
		for (countersnode_t *node = ctrs->head; node != NULL; node = node->next) {
			(*itemfunc)(arg, node->key, node->count);
		}
	}
}

You’ll need this for Lab 6!

Solution

counters_intersect-solution.c