(java1.3.1下通过)

import java.io.*;

class upstair{
    public static void main(String argc[]){
         int n=Integer.parseInt(argc[0]);
         int a[]=new int[n+1];
         int count=0;         
         int i,k;
         a[0]=-2;
         for(i=1;i<n+1;i++)
             a[i]=1;
         k=n;
         while(a[k]!=-1){
             if(sum(a)<n)  k++;
             if(sum(a)==n){
               for(i=1;i<=k;i++)
                   System.out.print(a[i]+" ");
                 System.out.println();
                 count++;
               a[k]=0;
               while(a[--k]==2)
                    a[k]=0;
             }  
             a[k]++;            
        }
        System.out.println(n+"级楼梯的走法:"+count);
     }    
    static int sum(int a[]){
        int sum=0;
        for(int i=1;i<a.length;i++)
            sum+=a[i];
       return sum;
    }
}