Tree- Depth first search

Author: AnushreeBagchi

depth-first-search-tree.py

@@ -0,0 +1,144 @@
+# post-order traversal
+
+class Node:
+    def __init__(self,value=None):
+        self.value = value
+        self.right = None
+        self.left = None
+    def set_value(self, value=None):
+        self.value = value
+    def get_value(self):
+        return self.value
+    def get_right_child(self):
+        return self.right
+    def get_left_child(self):
+        return self.left
+    def set_left_child(self, value):
+        self.left = value
+    def set_right_child(self, value):
+        self.right = value
+    def has_left_child(self):
+        return self.left != None
+    def has_right_child(self):
+        return self.right != None
+
+class Tree:
+    def __init__(self, value=None):
+        self.root = Node(value)
+    def get_root(self):
+        return self.root
+
+class State:
+    def __init__(self, node):
+        self.node = node
+        self.visited_left = False
+        self.visited_right = False
+    def get_node(self):
+        return self.node
+    def get_visited_left(self):
+        return self.visited_left
+    def get_visited_right(self):
+        return self.visited_right
+    def set_visited_left(self):
+        self.visited_left = True
+    def set_visited_right(self):
+        self.visited_right = True
+
+
+tree = Tree("apple")
+tree.get_root().set_left_child(Node("banana"))
+tree.get_root().set_right_child(Node("cherry"))
+tree.get_root().get_left_child().set_left_child(Node("dates"))
+
+class Stack:
+    def __init__(self):
+        self.list = list()
+    def push(self, value):
+        self.list.append(value)
+    def pop(self):
+        return self.list.pop()
+    def top(self):
+        if len(self.list) > 0:
+            return self.list[-1]
+        else:
+            return None
+    def is_empty(self):
+        return len(self.list) == 0
+
+     
+def pre_order_traversal_with_stack(tree):
+    stack = Stack()
+    visit_order = list()
+    node = tree.get_root()
+    state = State(node)
+    stack.push(state)
+    visit_order.append(node.get_value())
+    count = 0
+    while (node):
+        count+=1  
+        if node.has_left_child() and not state.get_visited_left():
+            state.set_visited_left()
+            node = node.get_left_child()
+            state = State(node)
+            stack.push(state)
+            visit_order.append(node.get_value())
+        elif node.has_right_child() and not state.get_visited_right():
+            state.set_visited_right()
+            node = node.get_right_child()
+            state = State(node)
+            stack.push(state)
+            visit_order.append(node.get_value())
+        else:
+            stack.pop()
+            if not stack.is_empty():
+                state = stack.top()
+                node = state.get_node()
+            else:
+                node = None
+    return visit_order
+def pre_order_traversal_with_recursion(tree):
+    node = tree.get_root()
+    visit_order = list()
+    def traverse(node):
+        if node:
+            # visit
+            visit_order.append(node.get_value())
+            # traverse left
+            traverse(node.get_left_child())
+            # traverse right
+            traverse(node.get_right_child())
+    traverse(node)
+    return visit_order
+def inorder_traversal_with_recursion(tree):
+    node = tree.get_root()
+    visit_order = list()
+    def traverse(node):
+        if node:
+            # traverse left
+            traverse(node.get_left_child())
+            # visit
+            visit_order.append(node.get_value())
+            # traverse right
+            traverse(node.get_right_child())
+    traverse(node)
+    return visit_order
+def post_order_traversal_with_recusrion(tree):
+    node = tree.get_root()
+    visit_order = list()
+    def traversal(node):
+        if node:
+            # traverse left
+            traversal(node.get_left_child())
+            # traverse right
+            traversal(node.get_right_child())
+            # visit
+            visit_order.append(node.get_value())
+    traversal(node)
+    return visit_order
+
+
+print(post_order_traversal_with_recusrion(tree))
+
+
+
+