题解 | #求int型正整数在内存中存储时1的个数#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int i = in.nextInt();
        StringBuilder sb = new StringBuilder();
        while (i / 2 > 0) {
            int n = i % 2;
            sb.append(n);
            i /= 2;
        }
        sb.append(i);
        sb.reverse();
        String s = sb.toString();
        int n = s.length() - s.replaceAll("1", "").length();
        System.out.println(n);
        // 不够优雅 
    }
}