#include <stdio.h>

/* The C Programming Language: 2nd Edition
 *
 * Exercise 1-14: Write a program to print a histogram of the frequencies of
 * different characters in its input.
 *
 * Answer: Using an array of characters (hint: that's what a string is) with
 * an array of ints is a good way to pair them up for counting. The 'i'
 * iterator variable ties to both so that lengths[i] represents the count for
 * chars[i].
 */

int main(void) {
	/* Rundown of variables:
	   c = current input char
	   ltrs = letter count
	   chars = string containing the characters the program will count
	   lengths = the counts for each character
	*/
	int c;
	int i = 0;
	char chars[] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
	/* cnum is the number of characters found in the above string */
	int cnum = 0;
	while (chars[i] != '\0') {
		cnum += 1;
		++i;
	}
	/* This array need its members to be initialized to zero. */
	int lengths[cnum];
	for (i = 0; i <= cnum; ++i) {
		lengths[i] = 0;
	}
	/* Capture input until it ends */
	while ((c = getchar()) != EOF) {
		for (i = 0; i < cnum; ++i) {
			if (c == chars[i]) {
				lengths[i] += 1;
			}
		}
	}
	/* This is ugly and I wish I knew a better way to do it. */
	printf("\nCHARACTER FREQUENCY\n\n         5   10   15   20   25   30   35   40   45   50   55   60   65   70   75\n");
	int iter = 0;
	while (iter <= cnum) {
		i = lengths[iter];
		if (i > 0) {
			printf("%2c | ", chars[iter]);
			while (i > 0) {
				printf("#");
				i -= 1;
			}
			printf("\n");
		}
		++iter;
	}
	return 0;
}