next_power_of_2.cpp

/*
 * Write a function that, for a given no n, finds a number p which is greater than or equal to n and is a power of 2.
 */
#include <iostream>

int next_power_of_2( int num ) {
  //already a power of 2
  if (num && !(num & (num-1))) {
    return num;
  }
  //count till msb set bit
  int count = 0;
  while ( num != 0 ) {
    num >>= 1;
    count++;
  }
  return (1 << count);
}

int main()
{
  std::cout << "Enter a number:";
  int num;
  std::cin >> num;
  std::cout << "Next power of 2 which is greater than or equal to " << num
            << " is: " << next_power_of_2(num) << std::endl;
  return 0;
}