LeetCode | Permutations

Given a collection of numbers, return all possible permutations.

For example,
[1,2,3] have the following permutations:
[1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1].

vector<vector<int> > permute(vector<int> &num) {
    vector<vector<int> > result;
    if (num.size() == 0) return result;

    std::sort(num.begin(), num.end());
    do {
        result.push_back(num);
    } while (std::next_permutation(num.begin(), num.end()));
    return result;        
}