Question

How to get the highest power of 2 that is less than or equal to N in C#

Answer 1

using System;

class Program
{
    static int highest_power_of_2_less_or_equal_to_n(int n) { 
        int power = 0; 
        for (int i = n; i >= 1; i--) { 
            // i == power of 2 ?
            if ((i & (i - 1)) == 0) { // 10 (1010) 9 (1001) 8 (1000) 7 (0111)
                power = i; 
                break; 
            } 
        } 
        return power; 
    } 
    static void Main()
    {
        int n = 17;
        Console.WriteLine(highest_power_of_2_less_or_equal_to_n(n)); 
      
        n = 10;
        Console.WriteLine(highest_power_of_2_less_or_equal_to_n(n)); 
      
        n = 64;
        Console.WriteLine(highest_power_of_2_less_or_equal_to_n(n)); 
    }
}


/*
run:

16
8
64

*/

 

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