title: Count Sum Of Digits In Numbers From 1 To N
signature: func countSumOfDigitsInNumbersFrom1ToN(n int) int {
test_code: package main
  
  import (
      "fmt"
      "reflect"
      "math"
      "sort"
  )
  
  // SOLUTION CODE
  // ===================================
  PLACEHOLDER_CODE_BODY
  
  // TESTING CODE
  // ===================================
  func validateSolution(actual int, expected int) bool {
      return reflect.DeepEqual(actual,expected)
  }
  
  func driver(n int, expected int) string {
      if validateSolution(PLACEHOLDER_FN_NAME(n),expected) {
              return "PASSED"
      }
      return "FAILED"
  
  }
  
  func main() {
  
      // Use imports to avoid undefined errors
      var _ = reflect.DeepEqual
      _ = math.Abs
      _ = sort.Sort
      result := ""
      result = driver(29, 165)
      fmt.Printf("TEST-0...%s\n", result)
      
      result = driver(97, 865)
      fmt.Printf("TEST-1...%s\n", result)
      
      result = driver(71, 540)
      fmt.Printf("TEST-2...%s\n", result)
      
      result = driver(82, 667)
      fmt.Printf("TEST-3...%s\n", result)
      
      result = driver(69, 525)
      fmt.Printf("TEST-4...%s\n", result)
      
      result = driver(30, 168)
      fmt.Printf("TEST-5...%s\n", result)
      
      result = driver(82, 667)
      fmt.Printf("TEST-6...%s\n", result)
      
      result = driver(32, 177)
      fmt.Printf("TEST-7...%s\n", result)
      
      result = driver(77, 609)
      fmt.Printf("TEST-8...%s\n", result)
      
      result = driver(39, 240)
      fmt.Printf("TEST-9...%s\n", result)
      
          
  }
source_py: def count_sum_of_digits_in_numbers_from_1_to_n(n):
      if (n < 10):
          return ((n * (n + 1)) / 2)
      d = int(math.log10(n))
      a = ([0] * (d + 1))
      a[0] = 0
      a[1] = 45
      for i in range(2, (d + 1)):
          a[i] = ((a[(i - 1)] * 10) + (45 * int(math.ceil(math.pow(10, (i - 1))))))
      p = int(math.ceil(math.pow(10, d)))
      msd = (n // p)
      return int(((((msd * a[d]) + (((msd * (msd - 1)) // 2) * p)) + (msd * (1 + (n % p)))) + count_sum_of_digits_in_numbers_from_1_to_n((n % p))))
source_cpp: int count_sum_of_digits_in_numbers_from_1_to_n(int n) {
    if ( n < 10 ) return n * ( n + 1 ) / 2;
    int d = log10 ( n );
    int * a = new int [ d + 1 ];
    a [ 0 ] = 0, a [ 1 ] = 45;
    for ( int i = 2;
    i <= d;
    i ++ ) a [ i ] = a [ i - 1 ] * 10 + 45 * ceil ( pow ( 10, i - 1 ) );
    int p = ceil ( pow ( 10, d ) );
    int msd = n / p;
    return msd * a [ d ] + ( msd * ( msd - 1 ) / 2 ) * p + msd * ( 1 + n % p ) + count_sum_of_digits_in_numbers_from_1_to_n ( n % p );
  }