int solution(vector<int> &A) {
    /*  If Vector A is empty then return 0  */
    if (A.size() == NULL)
        return 0;

    bool status = NULL; //initialize in first loop below
    int i = 1;
    int CriticalPoints = 1; // count of all critical points
    /*  Loop to search second critical point and initialize first (bool)status  */
    for (; i < A.size(); i++)
    {
        if (A[i] > A[i-1])
        {
            status = 1;// True if hill
            CriticalPoints++;
            break;
        }
        if (A[i] < A[i - 1])
        {
            status = 0;//False if valley
            CriticalPoints++;
            break;
        }
    }
    /*  If first loop end without break and 'i' is equal size of vector A, then
    all items in this vector have this same value, so return CriticalPoints (== 1)  */
    if (i == A.size())
        return CriticalPoints;
    /*  Else, search all critical points in this vector and return their count  */
    for (; i < A.size(); i++)
    {
        if ((status && A[i] < A[i - 1]) || (!status && A[i] > A[i - 1]))
        {
            CriticalPoints++;
            status = !status;
        }
    }

    return CriticalPoints;
}