90. 子集 II

package leetcode;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class demo_99 {
    public List<List<Integer>> subsetsWithDup(int[] nums) {
        Arrays.sort(nums);
        int visited[]=new int[nums.length];
        List<List<Integer>> list=new ArrayList<List<Integer>>();
        //设置每次要找的子集的长度
        for(int n=0;n<=nums.length;n++) {
            backtrack(list, new ArrayList<Integer>(), nums, n, visited,0);
        }
        System.out.println(list);
        return list;
    }
    //回溯法找子集
    public void backtrack(List<List<Integer>> list,List<Integer> li,int nums[],int n,int visited[],int start) {
        if(li.size()==n) {
            list.add(new ArrayList<Integer>(li));
        }
        else {
            for(int i=start;i<nums.length;i++) {
                if(visited[i]==1) {continue;}
                if(i>start&&nums[i]==nums[i-1]) {continue;}
                if(li.size()<n) {
                    visited[i]=1;
                    li.add(nums[i]);
                    backtrack(list, li, nums, n, visited,i+1);
                }
                visited[i]=0;
                li.remove(li.size()-1);
            }
        }
    }
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        demo_99 d99=new demo_99();
        int[] nums= {1,2,2};
        d99.subsetsWithDup(nums);
    }

}