deciHUA.c

#include <stdio.h>
#include <math.h>

#define ERR -1

int hua2dec(char *str) {
	long int res = 0;
	int len = strlen(str);
	if (str[0] != 'h' || str[len-1] != 'a') return ERR;
	
	int power = len-3;
	for (int i=1; i<=strlen(str)-2; i++) {
		if (str[i] == 'U') {
			res += ceil((int)pow(2, power));
			power--;
		} else if (str[i] == 'u') {
			power--;
		} else {
			return ERR;
		}	

	}
	return res;
}

int main () {
	printf("hUUuuuUua : %u\n", hua2dec("hUUuuuUua"));
	printf("huuUUuua  : %u\n", hua2dec("huuUUuua"));
	printf("huuuuUa   : %u\n", hua2dec("huuuuUa"));
	printf("hUUUUUa   : %u\n", hua2dec("hUUUUUa"));
	return 0;
}

numbers take the form hUuUuUua where 'h' and 'a' get removed, and the U's and u's get processed as 1's and 0's (respectively) in binary - returns in decimal form.