|
| 1 | +class Node: |
| 2 | + def __init__(self, data): |
| 3 | + self.data = data |
| 4 | + self.next = None |
| 5 | + |
| 6 | + |
| 7 | +class CircularLinkedList: |
| 8 | + def __init__(self): |
| 9 | + self.head = None |
| 10 | + |
| 11 | + def get_node(self, index): |
| 12 | + if self.head is None: |
| 13 | + return None |
| 14 | + current = self.head |
| 15 | + for i in range(index): |
| 16 | + current = current.next |
| 17 | + if current == self.head: |
| 18 | + return None |
| 19 | + return current |
| 20 | + |
| 21 | + def get_prev_node(self, ref_node): |
| 22 | + if self.head is None: |
| 23 | + return None |
| 24 | + current = self.head |
| 25 | + while current.next != ref_node: |
| 26 | + current = current.next |
| 27 | + return current |
| 28 | + |
| 29 | + def insert_after(self, ref_node, new_node): |
| 30 | + new_node.next = ref_node.next |
| 31 | + ref_node.next = new_node |
| 32 | + |
| 33 | + def insert_before(self, ref_node, new_node): |
| 34 | + prev_node = self.get_prev_node(ref_node) |
| 35 | + self.insert_after(prev_node, new_node) |
| 36 | + |
| 37 | + def insert_at_end(self, new_node): |
| 38 | + if self.head is None: |
| 39 | + self.head = new_node |
| 40 | + new_node.next = new_node |
| 41 | + else: |
| 42 | + self.insert_before(self.head, new_node) |
| 43 | + |
| 44 | + def insert_at_beg(self, new_node): |
| 45 | + self.insert_at_end(new_node) |
| 46 | + self.head = new_node |
| 47 | + |
| 48 | + def remove(self, node): |
| 49 | + if self.head.next == self.head: |
| 50 | + self.head = None |
| 51 | + else: |
| 52 | + prev_node = self.get_prev_node(node) |
| 53 | + prev_node.next = node.next |
| 54 | + if self.head == node: |
| 55 | + self.head = node.next |
| 56 | + |
| 57 | + def display(self): |
| 58 | + if self.head is None: |
| 59 | + return |
| 60 | + current = self.head |
| 61 | + while True: |
| 62 | + print(current.data, end = ' ') |
| 63 | + current = current.next |
| 64 | + if current == self.head: |
| 65 | + break |
| 66 | + |
| 67 | + |
| 68 | +a_cllist = CircularLinkedList() |
| 69 | + |
| 70 | +print('Menu') |
| 71 | +print('insert <data> after <index>') |
| 72 | +print('insert <data> before <index>') |
| 73 | +print('insert <data> at beg') |
| 74 | +print('insert <data> at end') |
| 75 | +print('remove <index>') |
| 76 | +print('quit') |
| 77 | + |
| 78 | +while True: |
| 79 | + print('The list: ', end = '') |
| 80 | + a_cllist.display() |
| 81 | + print() |
| 82 | + do = input('What would you like to do? ').split() |
| 83 | + |
| 84 | + operation = do[0].strip().lower() |
| 85 | + |
| 86 | + if operation == 'insert': |
| 87 | + data = int(do[1]) |
| 88 | + position = do[3].strip().lower() |
| 89 | + new_node = Node(data) |
| 90 | + suboperation = do[2].strip().lower() |
| 91 | + if suboperation == 'at': |
| 92 | + if position == 'beg': |
| 93 | + a_cllist.insert_at_beg(new_node) |
| 94 | + elif position == 'end': |
| 95 | + a_cllist.insert_at_end(new_node) |
| 96 | + else: |
| 97 | + index = int(position) |
| 98 | + ref_node = a_cllist.get_node(index) |
| 99 | + if ref_node is None: |
| 100 | + print('No such index.') |
| 101 | + continue |
| 102 | + if suboperation == 'after': |
| 103 | + a_cllist.insert_after(ref_node, new_node) |
| 104 | + elif suboperation == 'before': |
| 105 | + a_cllist.insert_before(ref_node, new_node) |
| 106 | + |
| 107 | + elif operation == 'remove': |
| 108 | + index = int(do[1]) |
| 109 | + node = a_cllist.get_node(index) |
| 110 | + if node is None: |
| 111 | + print('No such index.') |
| 112 | + continue |
| 113 | + a_cllist.remove(node) |
| 114 | + |
| 115 | + elif operation == 'quit': |
| 116 | + break |
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