parse tree

Author: ivanmmarkovic

README.md

@@ -75,6 +75,7 @@ but it also contains other data structures, algorithms and problems.
 ### [Trees]()
 - [List of lists representation](https://github.com/ivanmmarkovic/Problem-Solving-with-Algorithms-and-Data-Structures-using-Python/blob/master/trees/list-representation.py)
 - [Class representation](https://github.com/ivanmmarkovic/Problem-Solving-with-Algorithms-and-Data-Structures-using-Python/blob/master/trees/class-representation.py)
+- [Parse tree]()
 
 ### [Sorting](https://github.com/ivanmmarkovic/Problem-Solving-with-Algorithms-and-Data-Structures-using-Python/tree/master/sorting)
 - [Bubble sort](https://github.com/ivanmmarkovic/Problem-Solving-with-Algorithms-and-Data-Structures-using-Python/blob/master/sorting/bubble-sort.py)

trees/__pycache__/stack.cpython-38.pyc

@@ -0,0 +1,75 @@
+
+from stack import Stack
+import operator
+
+class TreeNode:
+    def __init__(self, key=None, left=None, right=None):
+        self.key = key
+        self.left = left
+        self.right = right
+
+    def insert_root_value(self, key=None):
+        self.key = key
+
+    def insert_left(self, key=None):
+        self.left = TreeNode(key, self.left)
+
+    def insert_right(self, key=None):
+        self.right = TreeNode(key, None, self.right)
+
+    def get_root_value(self):
+        return self.key
+
+    def get_left_child(self):
+        return self.left
+
+    def get_right_child(self):
+        return self.right
+
+
+opers = {'+':operator.add, '-':operator.sub, '*':operator.mul, '/':operator.truediv}
+
+import re
+pattern = re.compile("[0-9]")
+
+string = "( ( 10 + 5 ) * 3 )"
+
+
+def tree_parser(s: str) -> TreeNode:
+    arr: list = s.split()
+    stack: Stack = Stack()
+    node: TreeNode = TreeNode()
+    current_node: TreeNode = node
+    stack.push(node)
+    for e in arr:
+        if e == "(":
+            current_node.insert_left()
+            stack.push(current_node)
+            current_node = current_node.get_left_child()
+        elif e in "+-*/":
+            current_node.insert_root_value(e)
+            current_node.insert_right()
+            stack.push(current_node)
+            current_node = current_node.get_right_child()
+        elif pattern.match(e):
+            current_node.insert_root_value(int(e))
+            current_node = stack.pop()
+        elif e == ")":
+            current_node = stack.pop()
+        else:
+            raise Exception()
+    return node
+
+
+tree_node: TreeNode = tree_parser(string)
+
+
+def evaluate(node: TreeNode) -> int:
+    if node.get_left_child() is not None and node.get_right_child() is not None:
+        f = opers[node.get_root_value()]
+        return f(evaluate(node.get_left_child()), evaluate(node.get_right_child()))
+    else:
+        return node.get_root_value()
+
+
+print(evaluate(tree_node)) # 45

trees/parse-tree.py

@@ -0,0 +1,18 @@
+class Stack:
+    def __init__(self):
+        self.items = []
+
+    def is_empty(self):
+        return self.items == []
+
+    def push(self, item):
+        self.items.append(item)
+
+    def pop(self):
+        return self.items.pop()
+
+    def peek(self):
+        return self.items[len(self.items) - 1]
+
+    def size(self):
+        return len(self.items)