n&（n-1）n-1 应用

import java.util.Scanner;

public class Main {
    public static void main(String args[]) {
        Scanner cin = new Scanner(System.in);
        int l, r, m;
        while (cin.hasNextInt()) {
            l = cin.nextInt();
            r = cin.nextInt();
            m = cin.nextInt();
            int c = 0;
            //十进制数的范围
            for (int i = l; i <= r; i++) {
            //判断二进制中1的个数，并且记录次数
                if (getCount(i) == m) {
                    c++;
                }
            }
            //输出 判断如果c=0 c=-1，否则 c=c
            System.out.println(c == 0 ? -1 : c);
        }
    }

    private static int getCount(int n) {
        int i = 0;
        for (; n != 0; i++) {
            n = n & (n - 1);
        }
        return i;
    }
}