lanqiao 01字串 深度优先实现

public class Test008 {  
      
    private static int counter = 0;  
      
    public static void main(String[] args) {  
        int[] a = new int[5];  
          
        f(a, 0, 0);  
        f(a, 0, 1);  
          
        System.out.println(counter);  
    }  
      
    //a数组用来记录深度搜索暂时排列组合，index指向数组的下标，x是index指向的元素可能的取值  
    private static void f(int[] a, int index, int x){  
        a[index] = x;  
          
        if(index == 4){  
            System.out.println(p(a));  
            counter++;  
            return;  
        }  
          
        f(a, index+1, 0);  
        f(a, index+1, 1);  
    }  
      
    //将a数组变成字符串  
    private static String p(int[] a){  
        StringBuffer sb = new StringBuffer();  
        for (int i = 0; i < a.length; i++) {  
            int j = a[i];  
            sb.append(j);  
        }  
        return sb.toString();  
    }  
}