def is_sorted(items):
    """Return a boolean indicating whether given items are in sorted order.
    DONE: Running time: O(n), because the worst-case scenario would require 
    iterating through the entire array once.
    DONE: Memory usage: O(1), because the input array is modified in-place (if at all)."""
    # DONE: Check that all adjacent items are in order, return early if so
    for i in range(len(items) - 1):
        if items[i] > items[i+1]:
            return False
    return True