diff --git a/data-structures/zigzagtraversal_iterative.py b/data-structures/zigzagtraversal_iterative.py new file mode 100644 index 0000000..fa485b3 --- /dev/null +++ b/data-structures/zigzagtraversal_iterative.py @@ -0,0 +1,75 @@ +class Node: + """ + A Node has data variable and pointers to its left and right nodes. + """ + + def __init__(self, data): + self.left = None + self.right = None + self.data = data + +def make_tree() -> Node: + root = Node(1) + root.left = Node(2) + root.right = Node(3) + root.left.left = Node(4) + root.left.right = Node(5) + return root + +def zigzag_iterative(root: Node): + """ + ZigZag traverse by iterative method: Print node left to right and right to left, alternatively. + """ + if root == None: + return + + # two stacks to store alternate levels + s1 = [] # For levels to be printed from right to left + s2 = [] # For levels to be printed from left to right + + # append first level to first stack 's1' + s1.append(root) + + # Keep printing while any of the stacks has some nodes + while not len(s1) == 0 or not len(s2) == 0: + + # Print nodes of current level from s1 and append nodes of next level to s2 + while not len(s1) == 0: + temp = s1[-1] + s1.pop() + print(temp.data, end = " ") + + # Note that is left is appended before right + if temp.left: + s2.append(temp.left) + if temp.right: + s2.append(temp.right) + + # Print nodes of current level from s2 and append nodes of next level to s1 + while not len(s2) == 0: + temp = s2[-1] + s2.pop() + print(temp.data, end = " ") + + # Note that is rightt is appended before left + if temp.right: + s1.append(temp.right) + if temp.left: + s1.append(temp.left) + +def main(): # Main function for testing. + """ + Create binary tree. + """ + root = make_tree() + print("\nZigzag order traversal(iterative) is: ") + zigzag_iterative(root) + print() + + +if __name__ == "__main__": + import doctest + + doctest.testmod() + main() +