leetcode 047 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].

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class Solution {
public:
   bool generateNext(vector<int> &nums) {
		int len = nums.size(), i = 0, j = 0;

		for(i = len-2; i >= 0; i--) {
			if(nums[i] < nums[i+1]) break;
		}

		if(i < 0) return false;

		for(j = len-1; j > i; j--) {
			if(nums[j] > nums[i]) break;
		}

		int temp = nums[j];
		nums[j] = nums[i];
		nums[i] = temp;

		for(int l = i+1, r = len-1; l <= r; l++, r--) {
			temp = nums[r];
			nums[r] = nums[l];
			nums[l] = temp;
		}

		return true;
	}

	vector<vector<int> > permuteUnique(vector<int>& nums) {
		sort(nums.begin(), nums.end());
		vector<vector<int> > ans;
        ans.push_back(nums);
		while(generateNext(nums)) {
			ans.push_back(nums);
		}

		return ans;
	}
};