#include <stdio.h>
#define MAX 100000

int main ()
{
  int limit, n, num, maxH, h;
  int steps[MAX] = {}; // initialize array to all zeros

  // take input limit
  printf("How many numbers to check? ");
  scanf("%d", &limit);

  printf("\nCollatz Sequences:\n");
  for ( n = 0; n < limit; ++n ) {
    num = n+1; // n-th number is n+1
    while ( num > 1 ) { // generate the collatz sequence for a number
      printf("%d -> ", num);
      if ( num % 2 ) num = 3 * num + 1; // odd case
      else           num = num / 2;     // even case
      ++steps[n]; // calculate number of steps to converge to 1
    }
    printf("1\n");
  }

  printf("\nThe Histogram:\n");
  // find maximum height/steps
  maxH = steps[0];
  for ( n = 1; n < limit; ++n )
    if ( maxH < steps[n] )
      maxH = steps[n];

  for ( n = 0; n < limit; ++n ) // print a horizontal line
    printf("----");
  printf("\n");

  for ( h = maxH; h > 0; --h ) { // for each row upto maxH
    for ( n = 0; n < limit; ++n ) { // for each column upto limit
      if ( h > steps[n] ) printf("    "); // histogram below this h, so space to be printed
      else                printf("  H "); // histogram till or above this h, so H to be printed
    }
    printf("\n");
  }
  for ( n = 0; n < limit; ++n ) // print a horizontal line
    printf("----");
  printf("\n");
  for ( n = 0; n < limit; ++n ) // print the numbers
    printf(" %2d ", n+1);
  printf("\n");
  for ( n = 0; n < limit; ++n ) // print the number of steps taken to converge
    printf("(%2d)", steps[n]);
  printf("\n");

  return 0;
}