package LeetCode;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;

//使用HashMap进行计数

public class PermutationsII {

private List<List<Integer>> res=new ArrayList<>();

public List<List<Integer>> permuteUnique(int[] nums){

HashMap<Integer,Integer>count=new HashMap<>();

for(int i=0;i<nums.length;i++){

if(count.containsKey(nums[i])){

count.put(nums[i],count.get(nums[i])+1);

}else{

count.put(nums[i],1);

}

}

helper(nums,new ArrayList<>(),count);

return res;

}

public void helper(int[] nums,List<Integer> list,HashMap<Integer,Integer> count){

if(list.size()==nums.length){

res.add(new ArrayList<>(list));

return;

}

for(Integer i:count.keySet()){

if(count.get(i)>0){

list.add(i);

count.put(i,count.get(i)-1);

helper(nums,list,count);

count.put(i, count.get(i) + 1);

list.remove(list.size()-1);

}

}

}

}