01929-concatenation-of-array.cpp

/* easy :: array */
/*
    Resize by 2 and concat array.
    - -       - -
    Time  :: O(n)
    Space :: O(n)
*/
class Solution {
public:
    vector<int> getConcatenation(vector<int>& nums)
    {
        int n = (int)nums.size();
        nums.resize(2*n);
        for (int i = 0; i < n; ++i) {
            nums[i+n] = nums[i];
        }
        return nums;
    }
};