Data structure (Python)

# Course: CS261 - Data Structures # Student Name: # Assignment: # Description: class SLLException(Exception): """ Custom exception class to be used by Singly Linked List DO NOT CHANGE THIS CLASS IN ANY WAY """ pass class SLNode: """ Singly Linked List Node class DO NOT CHANGE THIS CLASS IN ANY WAY """ def __init__(self, value: object) -> None: self.next = None self.value = value class LinkedList: def __init__(self, start_list=None): """ Initializes a new linked list with front and back sentinels DO NOT CHANGE THIS METHOD IN ANY WAY """ self.head = SLNode(None) self.tail = SLNode(None) self.head.next = self.tail # populate SLL with initial values (if provided) # before using this feature, implement add_back() method if start_list is not None: for value in start_list: self.add_back(value) def __str__(self) -> str: """ Return content of singly linked list in human-readable form DO NOT CHANGE THIS METHOD IN ANY WAY """ out = 'SLL [' if self.head.next != self.tail: cur = self.head.next.next out = out + str(self.head.next.value) while cur != self.tail: out = out + ' -> ' + str(cur.value) cur = cur.next out = out + ']' return out def length(self) -> int: """ Return the length of the linked list DO NOT CHANGE THIS METHOD IN ANY WAY """ length = 0 cur = self.head while cur.next != self.tail: cur = cur.next length += 1 return length def is_empty(self) -> bool: """ Return True is list is empty, False otherwise DO NOT CHANGE THIS METHOD IN ANY WAY """ return self.head.next == self.tail # ------------------------------------------------------------------ # def add_front(self, value: object) -> None: """ TODO: Write this implementation """ # create a new node with value node = SLNode(value) # set next of node to next of head node.next = self.head.next # set next of head to node self.head.next = node pass def add_back(self, value: object) -> None: """ TODO: Write this implementation """ # create a new node with value node = SLNode(value) cur = self.head.next # set cur to first node of the list pre = self.head # set pre to node before cur # loop over the list to get the last node while cur != self.tail: pre = cur cur = cur.next # set next of pre to node pre.next = node # set next of node to back tail node.next = self.tail # traverse the list to find last node pass def insert_at_index(self, index: int, value: object) -> None: """ TODO: Write this implementation """ pass def remove_front(self) -> None: """ TODO: Write this implementation """ pass def remove_back(self) -> None: """ TODO: Write this implementation """ pass def remove_at_index(self, index: int) -> None: """ TODO: Write this implementation """ pass def get_front(self) -> object: """ TODO: Write this implementation """ pass def get_back(self) -> object: """ TODO: Write this implementation """ pass def remove(self, value: object) -> bool: """ TODO: Write this implementation """ pass def count(self, value: object) -> int: """ TODO: Write this implementation """ pass def slice(self, start_index: int, size: int) -> object: """ TODO: Write this implementation """ pass if __name__ == '__main__': pass print('\n# add_front example 1') list = LinkedList() print(list) list.add_front('A') list.add_front('B') list.add_front('C') print(list) # # print('\n# add_back example 1') list = LinkedList() print(list) list.add_back('C') list.add_back('B') list.add_back('A') print(list) # # print('\n# insert_at_index example 1') list = LinkedList() test_cases = [(0, 'A'), (0, 'B'), (1, 'C'), (3, 'D'), (-1, 'E'), (5, 'F')] for index, value in test_cases: print('Insert of', value, 'at', index, ': ', end='') try: list.insert_at_index(index, value) print(list) except Exception as e: print(type(e)) # # # print('\n# remove_front example 1') # list = LinkedList([1, 2]) # print(list) # for i in range(3): # try: # list.remove_front() # print('Successful removal', list) # except Exception as e: # print(type(e)) # # # print('\n# remove_back example 1') # list = LinkedList() # try: # list.remove_back() # except Exception as e: # print(type(e)) # list.add_front('Z') # list.remove_back() # print(list) # list.add_front('Y') # list.add_back('Z') # list.add_front('X') # print(list) # list.remove_back() # print(list) # # # print('\n# remove_at_index example 1') # list = LinkedList([1, 2, 3, 4, 5, 6]) # print(list) # for index in [0, 0, 0, 2, 2, -2]: # print('Removed at index:', index, ': ', end='') # try: # list.remove_at_index(index) # print(list) # except Exception as e: # print(type(e)) # print(list) # # # print('\n# get_front example 1') # list = LinkedList(['A', 'B']) # print(list.get_front()) # print(list.get_front()) # list.remove_front() # print(list.get_front()) # list.remove_back() # try: # print(list.get_front()) # except Exception as e: # print(type(e)) # # # print('\n# get_back example 1') # list = LinkedList([1, 2, 3]) # list.add_back(4) # print(list.get_back()) # list.remove_back() # print(list) # print(list.get_back()) # # # print('\n# remove example 1') # list = LinkedList([1, 2, 3, 1, 2, 3, 1, 2, 3]) # print(list) # for value in [7, 3, 3, 3, 3]: # print(list.remove(value), list.length(), list) # # # print('\n# count example 1') # list = LinkedList([1, 2, 3, 1, 2, 2]) # print(list, list.count(1), list.count(2), list.count(3), list.count(4)) # # # print('\n# slice example 1') # list = LinkedList([1, 2, 3, 4, 5, 6, 7, 8, 9]) # ll_slice = list.slice(1, 3) # print(list, ll_slice, sep="\n") # ll_slice.remove_at_index(0) # print(list, ll_slice, sep="\n") # # # print('\n# slice example 2') # list = LinkedList([10, 11, 12, 13, 14, 15, 16]) # print("SOURCE:", list) # slices = [(0, 7), (-1, 7), (0, 8), (2, 3), (5, 0), (5, 3), (6, 1)] # for index, size in slices: # print("Slice", index, "/", size, end="") # try: # print(" --- OK: ", list.slice(index, size)) # except: # print(" --- exception occurred.")