https://www.hackerrank.com/challenges/gem-stones

gemstones.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <math.h>
#include <assert.h>
#include <ctype.h>
int main(int argc, char const *argv[])
{
	int n,i,len,pint,ref[27][2]={0},elementcount=0;
	char a[111];
	scanf("%d", &n);
	pint=n;
	while(n--)
	{
		scanf("%s", a);
		len=strlen(a);
		for (i = 0; i < len; ++i)
			if (ref[a[i]-'a'][0]==0)
				ref[a[i]-'a'][0]++;
		for (i = 0; i < 27; ++i)
		{
			ref[i][1]+=ref[i][0];
			ref[i][0]=0;
		}
	}
	for (i = 0; i < 27; ++i)
		if (ref[i][1]==pint)
			elementcount++;
	printf("%d\n", elementcount);
	return 0;
}