//////////////////////////////////////////
// My Solution
/////////////////////////////////////////
vector<vector<int>> permute(vector<int>& nums) {

    if (nums.size() == 0) return vector<vector<int>>();

    sort(begin(nums), end(nums));
    vector<vector<int>> ret;
    ret.push_back(nums);

    // next permutation
    while (true)
    {
        int i = nums.size() - 2;
        while (i>=0 && nums[i] >= nums[i+1]) i--;

        if (i < 0)
        {
            // no more permutations.
            break;
        }

        int j = nums.size() - 1;
        while (i<j && nums[i] >= nums[j]) j--;

        swap(nums[i], nums[j]);

        int s = i + 1;
        int e = nums.size() -1;
        while (s < e)
            swap(nums[s++], nums[e--]);

        ret.push_back(nums);
    }

    return ret;
}