set difff in C

#include <stdio.h>
#include <stdlib.h>

void diffOfSets(char* setA, int lenA, char* setB, int lenB, char** setDiff, int* lenDiff)
{
    int *countDiff = malloc(sizeof(int) * 26);
    int *isIncludedArray = malloc(sizeof(int) * lenA);
    int includedItemCount = 0;
    
    for(int i=0;i<26;++i)
    {
        countDiff[i] = 0;
    }
    
    for(int i=0;i<lenA;++i)
    {
        countDiff[setA[i] - 'a']++;
    }

    for(int i=0;i<lenB;++i)
    {
        countDiff[setB[i] - 'a']--;
    }
    
    for(int i=0;i<26;++i)
    {
        if(countDiff[i] > 0)
        {
            includedItemCount++;
        }
    }

    *setDiff = (char *)malloc(sizeof(char) * includedItemCount);
    int addedItemCount = 0;    
    for(int i=0;i<26;++i)
    {
        if(countDiff[i] > 0)
        {
            (*setDiff)[addedItemCount] = i + 'a';
            addedItemCount++;
        }
    }
    
    *lenDiff = includedItemCount;
    /* O(mn) solution
    for(int i=0;i<lenA;++i)
    {
    	int isIncluded = 1;
    	printf("i = %d\n", i);
    	for(int j=0;j<lenB;++j)
    	{
    		printf("j = %d\n", j);
    		if(setA[i] == setB[j])
    		{
    			isIncluded = 0;
    			break;
    		}
    	}
    	
    	if(isIncluded == 1)
    	{
    		isIncludedArray[i] = 1;
    		includedItemCount++;
    	}
    }
    
    *setDiff = (char *)malloc(sizeof(char) * includedItemCount);
    int addedItemCount = 0;
    for(int i=0;i<lenA;++i)
    {
    	if(isIncludedArray[i] == 1)
    	{
    		(*setDiff)[addedItemCount] = setA[i];
    		addedItemCount++;
    	}
    }

    *lenDiff = includedItemCount;    
    */
}

int main(void) {
	char* ansArray;
	int ansCount;
	
	char A[] = {'z', 'c', 'f'};
	int countA = 3;
	char B[] = {'a', 'b', 'e', 'z'};
	int countB = 4;
	printf("ansArray = %x\n", ansArray);
	diffOfSets(A, countA, B, countB, &ansArray, &ansCount);
	
	for(int i=0;i<ansCount;++i)
	{
		printf("%c", ansArray[i]);
	}
	printf("\n");
	printf("%d\n", ansCount);
	
	return 0;
}