Solve BST Operations I in python

solutions/beecrowd/1200/1200.py

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+import sys
+
+add_space_before_letter = True
+
+
+class Node:
+    def __init__(self, letter=None, left=None, right=None):
+        self.letter = letter
+        self.left = left
+        self.right = right
+
+    def insert(self, new_node):
+        if not self.letter:
+            self.letter = new_node.letter
+            return
+
+        if self.letter > new_node.letter:
+            if self.right:
+                self.right.insert(new_node)
+            else:
+                self.right = new_node
+        else:
+            if self.left:
+                self.left.insert(new_node)
+            else:
+                self.left = new_node
+
+    def has(self, letter):
+        if self.letter == letter:
+            return True
+
+        result = False
+
+        if self.right and self.letter > letter:
+            result |= self.right.has(letter)
+        if self.left and self.letter < letter:
+            result |= self.left.has(letter)
+
+        return result
+
+    def __print(self):
+        global add_space_before_letter
+        if add_space_before_letter:
+            print(" ", end="")
+        print(self.letter, end='')
+        add_space_before_letter = True
+
+    def __traverse_print(self, traverse_type):
+        if traverse_type == 'PREFIX':
+            self.__print()
+        if self.right:
+            self.right.__traverse_print(traverse_type)
+        if traverse_type == 'INFIX':
+            self.__print()
+        if self.left:
+            self.left.__traverse_print(traverse_type)
+        if traverse_type == 'POSTFIX':
+            self.__print()
+
+    def prefix_print(self):
+        global add_space_before_letter
+        add_space_before_letter = False
+        self.__traverse_print(traverse_type='PREFIX')
+        print()
+
+    def infix_print(self):
+        global add_space_before_letter
+        add_space_before_letter = False
+        self.__traverse_print(traverse_type='INFIX')
+        print()
+
+    def postfix_print(self):
+        global add_space_before_letter
+        add_space_before_letter = False
+        self.__traverse_print(traverse_type='POSTFIX')
+        print()
+
+
+def main():
+    global add_space_before_letter
+    tree = Node(None, None, None)
+    for line in sys.stdin:
+        command, *args = (x.strip() for x in line.split(' '))
+        match [command, *args]:
+            case ['I', letter]:
+                tree.insert(Node(letter, None, None))
+            case ['P', letter]:
+                if tree.has(letter):
+                    print(f'{letter} existe')
+                else:
+                    print(f'{letter} nao existe')
+            case ['PREFIXA']:
+                tree.prefix_print()
+            case ['INFIXA']:
+                tree.infix_print()
+            case ['POSFIXA']:
+                tree.postfix_print()
+
+
+if __name__ == '__main__':
+    main()