# 1. Counting substrings.
# https://www.tutorialspoint.com/python3/string_count.htm


def count_substrings(haystack, needle):
    return haystack.count(needle)


print(count_substrings("This is a test string", "is"))
print(count_substrings("babababa", "baba"))
print(count_substrings("Python is an awesome language to program in!", "o"))
print(count_substrings("We have nothing in common!", "really?"))
print(count_substrings("This is this and that is this", "this"))


# 2. Sum numbers in matrix
# http://www.u.arizona.edu/~erdmann/mse350/topics/list_comprehensions.html


def sum_matrix(m):
    return sum(map(sum, m))


m = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
print(sum_matrix(m))

m = [[0, 0, 0], [0, 0, 0], [0, 0, 0]]
print(sum_matrix(m))

m = [[1, 2], [3, 4], [5, 6], [7, 8], [9, 10]]
print(sum_matrix(m))


# 3. NaN Expand

def nan_expand(times):
    return "{}{}".format("Not a " * times, "NaN" if times != 0 else "")


print(nan_expand(0))
print(nan_expand(1))
print(nan_expand(2))
print(nan_expand(3))


# 4. Integer prime factorization


def prime_factors(n):
    prfac = []
    d = 2
    times = 0
    while d * d <= n:
        if n % d == 0:
            while (n % d) == 0:
                times += 1
                n //= d
            prfac.append((d, times))
        d += 1
        times = 0
    if n > 1:
        prfac.append((n, 1))
    return prfac


print(prime_factors(1000))


# 5. https://docs.python.org/3/library/itertools.html

def max_concecutive(items):
    from itertools import groupby

    return max(sum(1 for i in g) for k, g in groupby(items))


print(max_concecutive([1, 2, 3, 3, 3, 3, 4, 3, 3]))
# 6. https://docs.python.org/3/library/itertools.html


def group(elem):
    from itertools import groupby

    return [list(grp) for k, grp in groupby(elem)]



print(group([1, 1, 1, 2, 3, 1, 1]))


# 7.

def first_max(curr, rest, tank_size):
    for x in rest:
        if tank_size < x - curr:
            return rest.index(x) - 1


def gas_stations(distance, tank_size, stations):
    stations.insert(0, 0)
    currentst = 0
    st = []
    current = 0

    while current >= stations[-1]:
        x = first_max(current, stations[currentst:], tank_size)
        print((stations[x + current]))
    return st


print(gas_stations(320, 90, [50, 80, 140, 180, 220, 290]))