#include <stdint.h>

char phrase1[] = "aeiou";
char phrase2[] = "a ee iii oooo uuuuu";

#define SIZE 5

uint16_t occurrences1[SIZE];
uint16_t occurrences2[SIZE];
uint16_t occurrences3[SIZE];


#if 0

int16_t find_vowel(char letter)
{
	switch (letter) {
		case 'a':
			return 0;
		case 'e':
			return 1;
		case 'i':
			return 2;
		case 'o':
			return 3;
		case 'u':
			return 4;
		default:
			return -1;
	}
}

#endif

#if 1

int16_t find_vowel(char letter)
{
	int16_t result = -1;
	switch (letter) {
		case 'a':
			result = 0;
			break;
		case 'e':
			result = 1;
			break;
		case 'i':
			result = 2;
			break;
		case 'o':
			result = 3;
			break;
		case 'u':
			result = 4;
	}
	return result;
}

#endif

void histogram_vowel(char phrase[], uint16_t max_letters, uint16_t occurrences[5])
{
	for (uint16_t i = 0; phrase[i] != '\0' && i < max_letters; i++) {
		int16_t idx;
		if ((idx = find_vowel(phrase[i])) != -1)
			occurrences[idx]++;
	}
}

int main(void)
{
	histogram_vowel(phrase1, 15, occurrences1);
	histogram_vowel(phrase2, 19, occurrences2);
	histogram_vowel("Hello world", 7, occurrences3);
}