top button
Flag Notify
    Connect to us
      Site Registration

Site Registration

How to count number of squares on a chessboard type n*n board using a C program?

+4 votes
505 views

Say you are given a 2X2 board then number of squares are 5. Can someone help with the logic and sample program?

posted Mar 13, 2016 by anonymous

Share this question
Facebook Share Button Twitter Share Button LinkedIn Share Button
I think its pretty straight forward, logic is -
1^2+2^2+...+n^2

1 Answer

+3 votes
 
Best answer

Below is C++ implementation of above formula. Since the value of n*(n+1)*(2n+1) can cause overflow for large values of n, below are some interesting tricks used in the program.
1) long int is used in return.
2) n * (n + 1) / 2 is evaluated first as the value n*(n+1) will always be a multiple of 2.
Note that overflow may still happen, but above tricks just reduce chances of overflow.

#include <iostream>
using namespace std;

// Function to return count of squares;
long int countSquares(int n)
{
    // A better way to write n*(n+1)*(2n+1)/6
    return (n * (n + 1) / 2) * (2*n + 1) / 3;
}

int main()
{
  int n = 4;
  cout << "Count of squares is " << countSquares(n);
  return 0;
}
answer Mar 13, 2016 by Amit Kumar Pandey
...