[LeetCode]047-Permutations II

题目：
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].

Solution：
直接运用nextPermutation的思想。nextPermutation，按照字典序排序的，字符串的下一个字典序全排列。

class Solution {
public:
    void nextPermutation(vector<int>& nums)
    {
        int  N = nums.size();

        int i = N - 1;

        while(i > 0 && (nums[i-1] >= nums[i]))
            i--;

        int j = i;
        while( j < N && i != 0 && nums[j] >nums[i-1])
            j++;

        if(i == 0)
            reverse(nums.begin(),nums.end());
        else
        {
            swap(nums[i-1],nums[j-1]);
            reverse(nums.begin()+i,nums.end());
        }
    }
    vector<vector<int>> permuteUnique(vector<int>& nums) {

        vector<vector<int>> ret;
        vector<int> temp = nums;
        ret.push_back(temp);
        nextPermutation(temp);
        while(temp != nums)
        {
            ret.push_back(temp);

            nextPermutation(temp);
        }
        return ret;
    }
};