【leetcode】Permutations II

Permutations II

Given a collection of numbers that might contain duplicates, return all possible unique permutations.

For example,
[1,1,2] have the following unique permutations:
[1,1,2], [1,2,1], and [2,1,1].

 

先排序，如果一个元素与上一个元素相等，且前面没有使用该元素，则该元素不参与当前排列

 

 class Solution {
 public:
     vector<vector<int> > permuteUnique(vector<int> &num) {

         sort(num.begin(),num.end());
         vector<vector<int> > result;
         vector<int> tmp;
         vector<bool> visited(num.size());
         dfs(,num,result,visited,tmp);
         return result;

     }

     void dfs(int level,vector<int> &num,vector<vector<int> > &result,vector<bool> &visited,vector<int> &tmp)
     {
         if(level==num.size())
         {
             result.push_back(tmp);
             return;
         }

         for(int i=;i<num.size();i++)
         {
             if(!visited[i])
             {
                 if(i>=&&((num[i]==num[i-]&&visited[i-])||(num[i]!=num[i-]))||i==)
                 {
                     visited[i]=true;
                     tmp.push_back(num[i]);
                     dfs(level+,num,result,visited,tmp);
                     tmp.pop_back();
                     visited[i]=false;
                 }
             }
         }
     }

 };