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].

void get(vector<int> &num, int index, vector<vector<int>> &solution)
	{
		if(index >= num.size())
		{
			solution.push_back(num);
			return;
		}else
			for(int i = index; i < num.size(); i++)
			{
				swap(num[index],num[i]);
				get(num,index+1,solution);
				swap(num[index],num[i]);
			}
	}
	vector<vector<int>> permute(vector<int> &num) {
        // Note: The Solution object is instantiated only once.
        vector<vector<int>> solution;
		if(num.size()<1)return solution;
		get(num, 0, solution);
		return solution;
    }