Merge pull request #182 from dsrao711/issue_180

Python solution for deleting a node in BST - DSA 450

Author: smv1999

DSA 450 GFG/DeleteNodeinBST.py

@@ -0,0 +1,50 @@
+#https://leetcode.com/problems/delete-node-in-a-bst/submissions/
+
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+class Solution:
+  
+    def findMinimum(self , root):
+      current = root
+      while(current.left):
+        current = current.left
+      return current
+      
+    def deleteNode(self, root: TreeNode, key: int) -> TreeNode:
+      
+      if not root:
+        return root
+      
+      
+      elif(key < root.val):
+        root.left = self.deleteNode(root.left , key)
+        
+      elif(key > root.val):
+        root.right = self.deleteNode(root.right , key)
+        
+      else:
+        
+        #Leaf
+        if not root.left and not root.right:
+          root = None
+        
+        #1 child   
+        elif not root.left:
+          root = root.right
+          
+        elif not root.right :
+          root = root.left
+          
+        #2 child
+        else:
+          temp = self.findMinimum(root.right)
+          root.val = temp.val
+          root.right = self.deleteNode(root.right , temp.val)
+          
+      return root
+        
+