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## Credit: https://www.geeksforgeeks.org/a-program-to-check-if-a-binary-tree-is-bst-or-not/
## Python program to check if a binary tree is bst or not
INT_MAX = 4294967296
INT_MIN = -4294967296
# A binary tree node
class Node:
# Constructor to create a new node
def __init__(self, data):
self.data = data
self.left = None
self.right = None
# Returns true if the given tree is a binary search tree (efficient version)
def isBST(node):
return isBSTUtil(node, INT_MIN, INT_MAX)
# Retusn true if the given tree is a BST and its values
# >= min and <= max
def isBSTUtil(node, mini, maxi):
# An empty tree is BST
if node is None:
return True
# False if this node violates min/max constraint
if node.data < mini or node.data > maxi:
return False
# Otherwise check the subtrees recursively
# tightening the min or max constraint
return (isBSTUtil(node.left, mini, node.data - 1) and isBSTUtil(node.right, node.data + 1, maxi))
# Driver program to test above function
### Example 1
# root = Node(8)
# root.left = Node(5)
# root.right = Node(9)
# root.left.left = Node(4)
# root.left.right = Node(6)
root = Node(5)
root.left = Node(4)
root.right = Node(7)
root.left.left = Node(3)
root.left.right = Node(6)
if (isBST(root)):
print "1 as the given tree is a BST."
else:
print "0 as the given tree is a not BST."
# This code is contributed by Nikhil Kumar Singh (nickzuck_007)
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