Check for BST

GeeksforGeeks/check_for_bst.py

@@ -0,0 +1,108 @@
+"""
+Given a binary tree. Check whether it is a BST or not.
+
+Example 1:
+
+Input:
+    2
+ /    \
+1      3
+Output: 1
+
+Problem link :- 
+https://practice.geeksforgeeks.org/problems/check-for-bst/1/?company[]=Amazon&problemStatus=solved&problemType=functional&page=1&sortBy=submissions&query=company[]AmazonproblemStatussolvedproblemTypefunctionalpage1sortBysubmissions
+
+"""
+
+
+INT_MAX = 4294967296
+INT_MIN = -4294967296
+
+from collections import deque
+# Tree Node
+class Node:
+    def __init__(self, val):
+        self.right = None
+        self.data = val
+        self.left = None
+
+# Function to Build Tree   
+def buildTree(s):
+    #Corner Case
+    if(len(s)==0 or s[0]=="N"):           
+        return None
+
+    # Creating list of strings from input 
+    # string after spliting by space
+    ip=list(map(str,s.split()))
+
+    # Create the root of the tree
+    root=Node(int(ip[0]))                     
+    size=0
+    q=deque()
+
+    # Push the root to the queue
+    q.append(root)                            
+    size=size+1 
+
+    # Starting from the second element
+    i=1                                       
+    while(size>0 and i<len(ip)):
+        # Get and remove the front of the queue
+        currNode=q[0]
+        q.popleft()
+        size=size-1
+
+        # Get the current node's value from the string
+        currVal=ip[i]
+
+        # If the left child is not null
+        if(currVal!="N"):
+
+            # Create the left child for the current node
+            currNode.left=Node(int(currVal))
+
+            # Push it to the queue
+            q.append(currNode.left)
+            size=size+1
+        # For the right child
+        i=i+1
+        if(i>=len(ip)):
+            break
+        currVal=ip[i]
+
+        # If the right child is not null
+        if(currVal!="N"):
+
+            # Create the right child for the current node
+            currNode.right=Node(int(currVal))
+
+            # Push it to the queue
+            q.append(currNode.right)
+            size=size+1
+        i=i+1
+    return root
+
+
+def isBST(node):
+    return checkBST(node,INT_MIN,INT_MAX)
+
+def checkBST(node,mini,maxi):
+    if node==None:
+        return 1
+    else:
+        if node.data<=mini or node.data>=maxi:
+            return 0
+        else:
+            return (checkBST(node.left,mini,node.data) and checkBST(node.right,node.data,maxi))
+
+
+if __name__=="__main__":
+    t=int(input())
+    for _ in range(0,t):
+        s=input()
+        root=buildTree(s)
+        if isBST(root):
+            print(1) 
+        else:
+            print(0)