A computer science problem by Paola Ramírez

Computer Science Level 2

How many positive four digits numbers exist such that the sum of their digits is greater than 33?


The answer is 15.

Paola Ramírez by Paola Ramírez , 24, Mexico

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5 solutions 

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#include <iostream>
using namespace std;
int sum(int n)
{
  int s = 0;
  while(n)
  {
    s += n % 10;
    n -= (n % 10);
    n /= 10;
  }
  return s;
}
main()
{
  int i = 1000, s = 0;
  while(i++ < 10000)  if(sum(i) > 33) s++;
  cout << s;
}


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def sum(n):
  s = 0
  while n:
    s += n % 10
    n -= (n % 10)
    n /= 10
  return s
i = 1000
s = 0
while i < 10000:
  if sum(i) > 33:
    s += 1
  i += 1
print(s)

0 Helpful 0 Interesting 1 Brilliant 0 Confused
Paola Ramírez
May 20, 2016

This problem I solved with excel but also could be solved using combinatorics

1 Helpful 0 Interesting 0 Brilliant 0 Confused

How did you do it with Excel?

Adhiraj Dutta - 1 year, 5 months ago
Hasmik Garyaka
Sep 17, 2017

print (len ([i for i in range(1000,10000) if sum(map(int, str(i)))>33]))

0 Helpful 0 Interesting 0 Brilliant 0 Confused
Pablo Ruiz
Oct 13, 2016

A solution Carlos García and Pablo coded in Java

public class ProblemaPaolaBrilliant{ 

 public static void main(String []args){
    int contador=0;
    int suma;
    for (int i=1000;i<10000;i++){
        String x=""+i;
        String p=x.substring(0,1);
        String s=x.substring(1,2);
        String t=x.substring(2,3);
        String c=x.substring(3,4);
        suma= Integer.parseInt(p) + Integer.parseInt(s) + Integer.parseInt(t) + Integer.parseInt(c);
        if (suma>33){
            contador++;
        }

    }
    System.out.println(contador);

 }

}

0 Helpful 0 Interesting 0 Brilliant 0 Confused 
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def digit_sum(num):
  return sum(map(int, str(num)))

ctr = 0
for n in range(1000, 10000):
  if digit_sum(n) > 33:
    ctr += 1

print ctr

0 Helpful 0 Interesting 0 Brilliant 0 Confused

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