Sherlock and Cost

• Time : O(n)
• Space : O(1)

long long cost(vector<int> A) {
    long long small = 0, big = 0, n = A.size();
    for(int i = 1; i < n; i++) {
        auto nbig = max(big + abs(A[i - 1] - A[i]),small + abs(A[i] - 1));
        auto nsmall = big + abs(A[i - 1] - 1);
        big = nbig;
        small = nsmall;
    }
    return max(small, big);
}