Tutorial 1 - 7 February 2025

T1/Q1 - moveEvenItemsToBack_LL.py

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+class ListNode:
+    def __init__(self, item):
+        self.item = item
+        self.next = None
+
+class LinkedList:
+    def __init__(self):
+        self.size = 0
+        self.head = None
+
+    def printList(self):
+        cur = self.head
+        if not cur:
+            print("Empty")
+            return
+        while cur:
+            print(cur.item, end=" ")
+            cur = cur.next
+        print()
+
+    def removeAllItems(self):
+        self.head = None
+        self.size = 0
+
+    def findNode(self, index):
+        if index < 0 or index >= self.size:
+            return None
+        cur = self.head
+        while index > 0:
+            cur = cur.next
+            index -= 1
+        return cur
+
+    def insertNode(self, index, value):
+        if index < 0 or index > self.size:
+            return -1
+
+        newNode = ListNode(value)
+        if index == 0:  # Insert at the beginning
+            newNode.next = self.head
+            self.head = newNode
+        else:
+            prev = self.findNode(index - 1)
+            newNode.next = prev.next
+            prev.next = newNode
+
+        self.size += 1
+        return 0
+
+    def removeNode(self, index):
+        if index < 0 or index >= self.size:
+            return -1
+
+        if index == 0:  # Remove the first node
+            self.head = self.head.next
+        else:
+            prev = self.findNode(index - 1)
+            prev.next = prev.next.next
+
+        self.size -= 1
+        return 0
+
+def moveEvenItemsToBack(ll):
+    if ll.size < 2:
+        return
+
+    cur = ll.head
+    index = 0
+    for _ in range(ll.size):
+        if cur.item % 2 == 0:
+            even_value = cur.item
+            cur = cur.next
+            ll.removeNode(index)
+            ll.insertNode(ll.size, even_value)
+        else:
+            cur = cur.next
+            index += 1
+
+if __name__ == "__main__":
+    ll = LinkedList()
+
+    while True:
+        print("1: Insert an integer to the linked list:")
+        print("2: Move all even integers to the back of the linked list:")
+        print("0: Quit:")
+
+        choice = int(input("Please input your choice (1/2/0): "))
+
+        if choice == 1:
+            value = int(input("Input an integer that you want to add to the linked list: "))
+            ll.insertNode(ll.size, value)
+            print("The resulting linked list is:")
+            ll.printList()
+        elif choice == 2:
+            moveEvenItemsToBack(ll)
+            print("The resulting linked list after moving even integers to the back is:")
+            ll.printList()
+        elif choice == 0:
+            ll.removeAllItems()
+            break
+        else:
+            print("Choice unknown;")

T1/Q2 - moveMaxToFront_LL.py

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+class ListNode:
+    def __init__(self, item):
+        self.item = item
+        self.next = None
+
+class LinkedList:
+    def __init__(self):
+        self.size = 0
+        self.head = None
+
+def printList(ll):
+    cur = ll.head
+    if cur is None:
+        print("Empty")
+        return
+    while cur is not None:
+        print(cur.item, end=" ")
+        cur = cur.next
+    print()
+
+def findNode(ll, index):
+    if ll is None or index < 0 or index >= ll.size:
+        return None
+
+    temp = ll.head
+    while index > 0:
+        temp = temp.next
+        if temp is None:
+            return None
+        index -= 1
+
+    return temp
+
+def insertNode(ll, index, value):
+    if ll is None or index < 0 or index > ll.size:
+        return -1
+
+    new_node = ListNode(value)
+
+    if index == 0:  # Insert at the beginning
+        new_node.next = ll.head
+        ll.head = new_node
+    else:
+        pre = findNode(ll, index - 1)
+        if pre is None:
+            return -1
+        new_node.next = pre.next
+        pre.next = new_node
+
+    ll.size += 1
+    return 0
+
+def removeNode(ll, index):
+    if ll is None or index < 0 or index >= ll.size:
+        return -1
+
+    if index == 0:  # Remove the first node
+        ll.head = ll.head.next
+    else:
+        pre = findNode(ll, index - 1)
+        if pre is None or pre.next is None:
+            return -1
+        pre.next = pre.next.next
+
+    ll.size -= 1
+    return 0
+
+def removeAllItems(ll):
+    ll.head = None
+    ll.size = 0
+
+def moveMaxToFront(ll):
+    if ll.head is None or ll.head.next is None:  # Empty list or single node
+        return -1
+
+    pre_max = None
+    max_node = ll.head
+    cur = ll.head
+
+    while cur.next is not None:
+        if cur.next.item > max_node.item:
+            pre_max = cur
+            max_node = cur.next
+        cur = cur.next
+
+    if pre_max is None:  # Max node is already at the front
+        return 0
+
+    # Move the max node to the front
+    pre_max.next = max_node.next
+    max_node.next = ll.head
+    ll.head = max_node
+
+    return 0
+
+if __name__ == "__main__":
+    ll = LinkedList()
+
+    while True:
+        print("1: Insert an integer to the linked list:")
+        print("2: Move the largest stored value to the front of the list:")
+        print("0: Quit:")
+
+        choice = int(input("Please input your choice (1/2/0): "))
+
+        if choice == 1:
+            value = int(input("Input an integer that you want to add to the linked list: "))
+            insertNode(ll, ll.size, value)
+            print("The resulting linked list is:")
+            printList(ll)
+        elif choice == 2:
+            moveMaxToFront(ll)
+            print("The resulting linked list after moving the largest stored value to the front of the list is:")
+            printList(ll)
+        elif choice == 0:
+            removeAllItems(ll)
+            break
+        else:
+            print("Choice unknown.")

T1/Q3 - removeDuplicatesSortedLL.py

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+class ListNode:
+    def __init__(self, item):
+        self.item = item
+        self.next = None
+
+class LinkedList:
+    def __init__(self):
+        self.size = 0
+        self.head = None
+
+# Function to remove duplicates from a sorted linked list
+def remove_duplicates_sorted_ll(ll):
+    current = ll.head
+    if current is None:
+        return
+
+    while current.next is not None:
+        if current.item == current.next.item:
+            temp = current.next.next
+            current.next = temp
+            ll.size -= 1
+        else:
+            current = current.next
+
+def print_list(ll):
+    current = ll.head
+    if current is None:
+        print("Empty")
+        return
+
+    while current is not None:
+        print(current.item, end=" ")
+        current = current.next
+    print()
+
+def remove_all_items(ll):
+    current = ll.head
+    while current is not None:
+        temp = current.next
+        current = None
+        current = temp
+
+    ll.head = None
+    ll.size = 0
+
+def find_node(ll, index):
+    if ll is None or index < 0 or index >= ll.size:
+        return None
+
+    temp = ll.head
+    while index > 0:
+        temp = temp.next
+        if temp is None:
+            return None
+        index -= 1
+
+    return temp
+
+def insert_node(ll, index, value):
+    if ll is None or index < 0 or index > ll.size:
+        return -1
+
+    new_node = ListNode(value)
+
+    # If inserting at the head
+    if index == 0:
+        new_node.next = ll.head
+        ll.head = new_node
+        ll.size += 1
+        return 0
+
+    # Insert at other positions
+    prev_node = find_node(ll, index - 1)
+    if prev_node is not None:
+        new_node.next = prev_node.next
+        prev_node.next = new_node
+        ll.size += 1
+        return 0
+
+    return -1
+
+def remove_node(ll, index):
+    if ll is None or index < 0 or index >= ll.size:
+        return -1
+
+    # Remove head node
+    if index == 0:
+        ll.head = ll.head.next
+        ll.size -= 1
+        return 0
+
+    # Remove other nodes
+    prev_node = find_node(ll, index - 1)
+    if prev_node is not None and prev_node.next is not None:
+        prev_node.next = prev_node.next.next
+        ll.size -= 1
+        return 0
+
+    return -1
+
+if __name__ == "__main__":
+    ll = LinkedList()
+
+    while True:
+        print("1: Insert an integer to the linked list:")
+        print("2: Remove duplicates from a sorted linked list:")
+        print("0: Quit:")
+        choice = int(input("Please input your choice(1/2/0): "))
+
+        if choice == 1:
+            value = int(input("Input an integer that you want to add to the linked list: "))
+            insert_node(ll, ll.size, value)
+            print("The resulting linked list is: ")
+            print_list(ll)
+        elif choice == 2:
+            remove_duplicates_sorted_ll(ll)
+            print("The resulting linked list after removing duplicate values from the sorted linked list is: ")
+            print_list(ll)
+        elif choice == 0:
+            remove_all_items(ll)
+            break
+        else:
+            print("Choice unknown;")