Question

How to count the total set bits in all numbers from 1 to N in Java

Answer 1

import java.io.*;  
 
public class MyClass {
    static int count_set_bits(int n) { 
        int count = 0; 
        while (n > 0) { 
            count += n & 1; 
            n >>= 1; 
        } 
        return count; 
    }
    static int count_total_set_bits(int n) { 
        int setBitCount = 0; 
       
        for (int i = 1; i <= n; i++) 
            setBitCount += count_set_bits(i); 
       
        return setBitCount; 
    } 
    public static void main(String args[]) {
         int n = 6; 
         /* 0001
            0010
            0011
            0100
            0101
            0110 */

        System.out.println(count_total_set_bits(n)); 
    }
}
 
 
/*
run:
 
9
 
*/

 

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