import java.util.Scanner;
/**
 * 输出1的被选中。0的未被选中
 * @author
 *
 */

public class Choose {
    public static void showTeams(int[] array, int i, int chooseNum) {        
        if (i >= array.length) {
            int cnt = 0;
            for (int j = 0; j < array.length; ++j)
                cnt += array[j];
            if (cnt == chooseNum) {
                for (int j = 0; j < array.length; ++j)
                    System.out.print(array[j] + "  ");
                System.out.println();
            }
            return;
        }
        array[i] = 1;
        ++i;
        showTeams(array, i, chooseNum);
        array[i - 1] = 0;
        showTeams(array, i, chooseNum);
    }

    public static void main(String[] args) {
        int total, chooseNum;
        Scanner sc = new Scanner(System.in);
        total = sc.nextInt();
        chooseNum = sc.nextInt();
        int[] array = new int[total];
        for (int i = 0; i < array.length; ++i)
            array[i] = 0;
        showTeams(array, 0, chooseNum);
    }

}

------解决方案--------------------
Java code

这个是输出编号
mark[]里面放编号
import java.util.Scanner;



public class Choose {
    public static void showTeams(int[] array, int i, int chooseNum, int[] mark) {
        if (i >= array.length) {
            int cnt = 0;
            for (int j = 0; j < array.length; ++j)
                cnt += array[j];
            if (cnt == chooseNum) {
                for (int j = 0; j < array.length; ++j) {
                    if (array[j] == 1)
                        System.out.print(mark[j] + "  ");
                }
                System.out.println();
            }
            return;
        }
        array[i] = 1;
        ++i;
        showTeams(array, i, chooseNum, mark);
        array[i - 1] = 0;
        showTeams(array, i, chooseNum, mark);
    }

    public static void main(String[] args) {
        int total, chooseNum;
        Scanner sc = new Scanner(System.in);
        total = sc.nextInt();
        chooseNum = sc.nextInt();
        int[] array = new int[total];
        int[] mark = new int[total];
        for (int i = 0; i < array.length; ++i) {
            array[i] = 0;
            mark[i] = i + 1;
        }
        showTeams(array, 0, chooseNum, mark);
    }

}

------解决方案--------------------

我也来凑个热闹，
贴个用泛型的

Java code

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class ChooseMInN2 {
    static int total;
    static int need;
    static List<Integer> selected = new ArrayList<Integer>();
    
    public static void showTeams(int current ) {
        if (selected.size()==need){ //成功
            System.out.println(selected);
            return;
        }
        if (current>total) return; //失败
        showTeams(current+1); //不加当前元素，继续探索
        selected.add(current);
        showTeams(current+1); //加当前元素，继续探索
        selected.remove(new Integer(current)); //回溯
    }

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        total = sc.nextInt();
        need = sc.nextInt();
        showTeams(1);
    }

}

------解决方案--------------------

又是排列组合的问题，凑个热闹吧，递归和非递归写法
Java code