lab06.py

HW_SOURCE_FILE = __file__


def insert_items(lst, entry, elem):
    """Inserts elem into lst after each occurence of entry and then returns lst.

    >>> test_lst = [1, 5, 8, 5, 2, 3]
    >>> new_lst = insert_items(test_lst, 5, 7)
    >>> new_lst
    [1, 5, 7, 8, 5, 7, 2, 3]
    >>> double_lst = [1, 2, 1, 2, 3, 3]
    >>> double_lst = insert_items(double_lst, 3, 4)
    >>> double_lst
    [1, 2, 1, 2, 3, 4, 3, 4]
    >>> large_lst = [1, 4, 8]
    >>> large_lst2 = insert_items(large_lst, 4, 4)
    >>> large_lst2
    [1, 4, 4, 8]
    >>> large_lst3 = insert_items(large_lst2, 4, 6)
    >>> large_lst3
    [1, 4, 6, 4, 6, 8]
    >>> large_lst3 is large_lst
    True
    >>> # Ban creating new lists
    >>> from construct_check import check
    >>> check(HW_SOURCE_FILE, 'insert_items',
    ...       ['List', 'ListComp', 'Slice'])
    True
    """
    count = 0
    while len(lst) > count:
        if lst[count]==entry:
            lst.insert(count+1,elem)
            count+=2
        else:
            count+=1
    return lst


def count_occurrences(t, n, x):
    """Return the number of times that x appears in the first n elements of iterator t.

    >>> s = iter([10, 9, 10, 9, 9, 10, 8, 8, 8, 7])
    >>> count_occurrences(s, 10, 9)
    3
    >>> s2 = iter([10, 9, 10, 9, 9, 10, 8, 8, 8, 7])
    >>> count_occurrences(s2, 3, 10)
    2
    >>> s = iter([3, 2, 2, 2, 1, 2, 1, 4, 4, 5, 5, 5])
    >>> count_occurrences(s, 1, 3)
    1
    >>> count_occurrences(s, 4, 2)
    3
    >>> next(s)
    2
    >>> s2 = iter([4, 1, 6, 6, 7, 7, 8, 8, 2, 2, 2, 5])
    >>> count_occurrences(s2, 6, 6)
    2
    """
    num=0
    for i in range(n):
        if next(t)==x:
            num+=1
    return num


def repeated(t, k):
    """Return the first value in iterator T that appears K times in a row.
    Iterate through the items such that if the same iterator is passed into
    the function twice, it continues in the second call at the point it left
    off in the first.

    >>> s = iter([10, 9, 10, 9, 9, 10, 8, 8, 8, 7])
    >>> repeated(s, 2)
    9
    >>> s2 = iter([10, 9, 10, 9, 9, 10, 8, 8, 8, 7])
    >>> repeated(s2, 3)
    8
    >>> s = iter([3, 2, 2, 2, 1, 2, 1, 4, 4, 5, 5, 5])
    >>> repeated(s, 3)
    2
    >>> repeated(s, 3)
    5
    >>> s2 = iter([4, 1, 6, 6, 7, 7, 8, 8, 2, 2, 2, 5])
    >>> repeated(s2, 3)
    2
    """
    assert k > 1
    inFront = 0
    c = 0
    for value in t:
        if inFront == 0 or value == inFront:
            c+=1
            if c == k:
                return value
        else:
            c = 1
        inFront = value
    return 0