C++ Exercises: Compute the sum of the specified number of Prime numbers

C++ Basic: Exercise-75 with Solution

Write a C++ program to compute the sum of the specified number of Prime numbers.

For example when n = 7,
s = 2 + 3 + 5 + 7 + 11 + 13 + 17 = 58.

Pictorial Presentation:

Sample Solution:

C++ Code :

#include <iostream>
using namespace std;
 int main()
{
  const int MAX = 1000000;
  const int sqrtMAX = 1000;
  int n;
  int b[MAX+1] = {0};
  int i, j;
  int sum;
  int count;
  b[0] = 1;
  b[1] = 1;
  cin>> n;
  for(i=4; i<=MAX; i+=2)
      b[i] = 1;
  for(i=3; i<=sqrtMAX; i+=2)
      for(j=i+i; j<=MAX; j+=i)
          b[j] = 1;
 
      if(n == 0)
          return 0;
      sum = 0;
      count = 0;
      for(i=2; count<n; i++) {
        if(b[i]==0) {
              count++;
              sum+=i;
        }
    }
   cout << "Sum of the  first " << n << " Prime numbers is: " << sum;
  return 0;
}

Sample Output:

Sample Input: 7
Sum of the  first 7 Prime numbers is: 58

Flowchart:

C++ Code Editor:

Contribute your code and comments through Disqus.

Previous: Write a C++ program that accepts various numbers and compute the difference between the highest number and the lowest number. All input numbers should be real numbers between 0 and 1,000,000. The output (real number) may include an error of 0.01 or less.
Next: Write a C++ program that accept an integer (n) from the user and outputs the number of combinations that express n as a sum of two prime numbers.