115 lines
2.7 KiB
Python
115 lines
2.7 KiB
Python
class Bst_node:
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def __init__(self, item):
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self.item = item
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self.left = None
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self.right = None
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class Stack_node:
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def __init__(self, data):
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self.data = data
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self.next = None
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class Stack:
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def __init__(self):
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self.top = None
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def insert_bst_node(node_ref, value):
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if node_ref[0] is None:
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node_ref[0] = Bst_node(value)
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else:
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if value < node_ref[0].item:
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if node_ref[0].left is None:
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node_ref[0].left = Bst_node(value)
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else:
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insert_bst_node([node_ref[0].left], value)
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elif value > node_ref[0].item:
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if node_ref[0].right is None:
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node_ref[0].right = Bst_node(value)
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else:
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insert_bst_node([node_ref[0].right], value)
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def push(stack, node):
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temp = Stack_node(node)
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if stack.top is None:
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stack.top = temp
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temp.next = None
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else:
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temp.next = stack.top
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stack.top = temp
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def pop(s):
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if s.top is None:
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return None
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temp = s.top.next
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ptr = s.top.data
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s.top = temp
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return ptr
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def peek(s):
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if s.top is None:
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return None
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return s.top.data
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def isEmpty(s):
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return s.top is None
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def removeAll(node_ref):
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if node_ref[0] is not None:
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removeAll([node_ref[0].left])
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removeAll([node_ref[0].right])
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node_ref[0] = None
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def pre_order_iterative(root):
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stack = Stack()
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temp = root
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if temp is None:
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return
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push(stack, temp)
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while not isEmpty(stack):
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temp = pop(stack)
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print(temp.item, end=" ")
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if temp.right is not None:
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push(stack, temp.right)
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if temp.left is not None:
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push(stack, temp.left)
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def main():
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root = [None] # Using list to simulate pointer reference
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print("1: Insert an integer into the binary search tree;")
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print("2: Print the pre-order traversal of the binary search tree;")
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print("0: Quit;")
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while True:
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try:
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c = int(input("Please input your choice(1/2/0): "))
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if c == 1:
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i = int(input("Input an integer that you want to insert into the Binary Search Tree: "))
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insert_bst_node(root, i)
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elif c == 2:
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print("The resulting pre-order traversal of the binary search tree is: ", end="")
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pre_order_iterative(root[0])
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print()
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elif c == 0:
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removeAll(root)
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break
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else:
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print("Choice unknown;")
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except ValueError:
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print("Invalid input")
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continue
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if __name__ == "__main__":
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main() |