Task: Humble numbers




Go: package main

import (
    "fmt"
    "math/big"
)

var (
    one   = new(big.Int).SetUint64(1)
    two   = new(big.Int).SetUint64(2)
    three = new(big.Int).SetUint64(3)
    five  = new(big.Int).SetUint64(5)
    seven = new(big.Int).SetUint64(7)
    ten   = new(big.Int).SetUint64(10)
)

func min(a, b *big.Int) *big.Int {
    if a.Cmp(b) < 0 {
        return a
    }
    return b
}

func humble(n int) []*big.Int {
    h := make([]*big.Int, n)
    h[0] = new(big.Int).Set(one)
    next2, next3 := new(big.Int).Set(two), new(big.Int).Set(three)
    next5, next7 := new(big.Int).Set(five), new(big.Int).Set(seven)
    var i, j, k, l int
    for m := 1; m < len(h); m++ {
        h[m] = new(big.Int).Set(min(next2, min(next3, min(next5, next7))))
        if h[m].Cmp(next2) == 0 {
            i++
            next2.Mul(two, h[i])
        }
        if h[m].Cmp(next3) == 0 {
            j++
            next3.Mul(three, h[j])
        }
        if h[m].Cmp(next5) == 0 {
            k++
            next5.Mul(five, h[k])
        }
        if h[m].Cmp(next7) == 0 {
            l++
            next7.Mul(seven, h[l])
        }
    }
    return h
}

func commatize(n int) string {
    s := fmt.Sprintf("%d", n)
    le := len(s)
    for i := le - 3; i >= 1; i -= 3 {
        s = s[0:i] + "," + s[i:]
    }
    return s
}

func main() {
    const n = 13 * 1e6  
    h := humble(n) 
    fmt.Println("The first 50 humble numbers are:")
    fmt.Println(h[0:50])

    maxDigits := len(h[len(h)-1].String()) - 1
    counts := make([]int, maxDigits+1)
    var maxUsed int
    digits := 1
    pow10 := new(big.Int).Set(ten)
    for i := 0; i < len(h); i++ {
        for {
            if h[i].Cmp(pow10) >= 0 {
                pow10.Mul(pow10, ten)
                digits++
            } else {
                break
            }
        }  
        if digits > maxDigits {
            maxUsed = i
            break
        }
        counts[digits]++
    }
    fmt.Printf("\nOf the first %s humble numbers:\n", commatize(maxUsed))
    for i := 1; i <= maxDigits; i++ {
        s := "s"
        if i == 1 {
            s = ""
        }
        fmt.Printf("%9s have %2d digit%s\n", commatize(counts[i]), i, s)
    }       
}








Ada: with Ada.Text_IO;

procedure Show_Humble is

   type Positive is range 1 .. 2**63 - 1;
   First : constant Positive := Positive'First;
   Last  : constant Positive := 999_999_999;

   function Is_Humble (I : in Positive) return Boolean is
   begin
      if    I <= 1      then  return True;
      elsif I mod 2 = 0 then  return Is_Humble (I / 2);
      elsif I mod 3 = 0 then  return Is_Humble (I / 3);
      elsif I mod 5 = 0 then  return Is_Humble (I / 5);
      elsif I mod 7 = 0 then  return Is_Humble (I / 7);
      else                    return False;
      end if;
   end Is_Humble;

   subtype Digit_Range is Natural range First'Image'Length - 1 .. Last'Image'Length - 1;
   Digit_Count  : array (Digit_Range) of Natural := (others => 0);

   procedure Count_Humble_Digits is
      use Ada.Text_IO;
      Humble_Count : Natural := 0;
      Len : Natural;
   begin
      Put_Line ("The first 50 humble numbers:");
      for N in First .. Last loop
         if Is_Humble (N) then
            Len := N'Image'Length - 1;
            Digit_Count (Len) := Digit_Count (Len) + 1;

            if Humble_Count < 50 then
               Put (N'Image);
               Put (" ");
            end if;
            Humble_Count := Humble_Count + 1;
         end if;
      end loop;
      New_Line (2);
   end Count_Humble_Digits;

   procedure Show_Digit_Counts is
      package Natural_IO is
         new Ada.Text_IO.Integer_IO (Natural);
      use Ada.Text_IO;
      use Natural_IO;

      Placeholder : String := "Digits Count";
      Image_Digit : String renames Placeholder (1 .. 6);
      Image_Count : String renames Placeholder (8 .. Placeholder'Last);
   begin
      Put_Line ("The digit counts of humble numbers:");
      Put_Line (Placeholder);
      for Digit in Digit_Count'Range loop
         Put (Image_Digit, Digit);
         Put (Image_Count, Digit_Count (Digit));
         Put_Line (Placeholder);
      end loop;
   end Show_Digit_Counts;

begin
   Count_Humble_Digits;
   Show_Digit_Counts;
end Show_Humble;