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| 1 | + |
| 2 | +# Given a binary Tree |
| 3 | +# 1 |
| 4 | +# / \ |
| 5 | +# 2 3 |
| 6 | +# / \ / \ |
| 7 | +# 4 5 6 7 |
| 8 | +# Print zig-zag level order traversal |
| 9 | +# 1 3 2 4 5 6 7 |
| 10 | +# |
| 11 | + |
| 12 | +class TreeNode: |
| 13 | + def __init__(self, data): |
| 14 | + """Representation of a binary tree node""" |
| 15 | + self.data = data |
| 16 | + self.left = None |
| 17 | + self.right = None |
| 18 | + |
| 19 | + |
| 20 | +class Tree: |
| 21 | + def __init__(self): |
| 22 | + """Reprentation of a binary tree""" |
| 23 | + self.root = None |
| 24 | + |
| 25 | + def _print_level(self, node, level, zig): |
| 26 | + """Utility function to print the level, level starts with 1""" |
| 27 | + if node is None: |
| 28 | + return |
| 29 | + if level == 1: |
| 30 | + print(node.data, end=' ') |
| 31 | + return |
| 32 | + else: |
| 33 | + if zig: |
| 34 | + self._print_level(node.left, level-1, zig) |
| 35 | + self._print_level(node.right, level-1, zig) |
| 36 | + else: |
| 37 | + self._print_level(node.right, level-1, zig) |
| 38 | + self._print_level(node.left, level-1, zig) |
| 39 | + |
| 40 | + def _height(self, node): |
| 41 | + """Gets the height of the tree from node""" |
| 42 | + if node is None: |
| 43 | + return 0 |
| 44 | + else: |
| 45 | + return max(self._height(node.left), self._height(node.right)) + 1 |
| 46 | + |
| 47 | + def print_zig_zag(self): |
| 48 | + """Prints the zig zag level order""" |
| 49 | + if self.root is None: |
| 50 | + return |
| 51 | + h = self._height(self.root) |
| 52 | + zig = True |
| 53 | + for i in range(1, h+1): |
| 54 | + self._print_level(self.root, i, not zig) |
| 55 | + print() |
| 56 | + |
| 57 | + def in_order(self): |
| 58 | + """In order traversal of the tree""" |
| 59 | + current = self.root |
| 60 | + stack = [] |
| 61 | + done = False |
| 62 | + while not done: |
| 63 | + if current is not None: |
| 64 | + stack.append(current) |
| 65 | + current = current.left |
| 66 | + |
| 67 | + elif stack: |
| 68 | + current = stack.pop() |
| 69 | + print(current.data, end=' ') |
| 70 | + current = current.right |
| 71 | + else: |
| 72 | + done = True |
| 73 | + print() |
| 74 | + |
| 75 | +if __name__ == "__main__": |
| 76 | + tree = Tree() |
| 77 | + tree.root = TreeNode(1) |
| 78 | + tree.root.left = TreeNode(2) |
| 79 | + tree.root.right = TreeNode(3) |
| 80 | + tree.root.left.left = TreeNode(4) |
| 81 | + tree.root.left.right = TreeNode(5) |
| 82 | + tree.root.right.left = TreeNode(6) |
| 83 | + tree.root.right.right = TreeNode(7) |
| 84 | + |
| 85 | + print("In order:") |
| 86 | + tree.in_order() |
| 87 | + |
| 88 | + print("Zig zag level order:") |
| 89 | + tree.print_zig_zag() |
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