cs61a 2021 fall lab06

网址 https://inst.eecs.berkeley.edu/~cs61a/fa21/lab/lab06/#q5-repeated

    from re import I


    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
        """
        "*** YOUR CODE HERE ***"
        num = 0
        flag = 0
        for i in lst:
            if entry == elem:
                if flag == 1:
                    flag = 0
                    continue
            if i == entry:
                lst.insert(num + 1, elem)
                flag = 1
            num += 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
        """
        "*** YOUR CODE HERE ***"
        ans = 0
        for i in range(n):
            if next(t) == x:
                ans += 1
        return ans 

    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
        "*** YOUR CODE HERE ***"
        pre = -1
        ans = 1
        while 1 :
            if pre == -1:
                pre = next(t) 
            else:
                if ans == k:
                    return pre
                else:
                    i = next(t)
                    if i == pre:
                        ans += 1
                    else :
                        ans = 1
                    pre = i