leetcode103:permutations-ii

题目描述

给出一组可能包含重复项的数字，返回该组数字的所有排列

例如；

[1,1,2]的排列如下：
[1,1,2],[1,2,1], [2,1,1].

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].

class Solution {
    int array[19]={0};
    void permutation(vector<vector<int>> &ans ,vector<int> &num,int k,int n){
        if (k==n)
            ans.push_back(num);
        else
        {
            for (int i=0;i<19;i++){
                if (array[i]>0)
                {
                    array[i]--;
                    num[k]=i-9;
                    permutation(ans, num,  k+1,  n);
                    array[i]++;
                }
            }
        }
    }
public:
    vector<vector<int> > permuteUnique(vector<int> &num) {
        for (int i=0;i<num.size();i++){
            array[num[i]+9]++;
        }
        vector<vector<int>> ans;
        permutation(ans, num, 0, num.size());
        return ans;
    }
};