276. Paint Fence

class Solution {
public:
    int numWays(int n, int k) {
        if (n < 2) return k * n;
        int diff = k, same = 0; //you don't need arrays!!!!!!
        for (int i = 1; i < n; i++) {
            int tmp = diff;
            diff = (same + diff) * (k - 1);
            same = tmp;
        }
        return diff + same;
    }
};