day 8 LCA

Author: mandliya

README.md

@@ -7,10 +7,10 @@
 | Current Status|     Stats     |
 | :------------: | :----------: |
 | Total C++ Problems | 188 |
-| Total Python Problems | 11 |
+| Total Python Problems | 12 |
 | Current Daily Streak| 7 |
 | Last Streak | 06/20/2019 - 06/21/2019|
-| Current Streak | 06/23/2019 - 06/29/2019|
+| Current Streak | 06/23/2019 - 06/30/2019|
 
 </center>
 
@@ -119,7 +119,7 @@ Include contains single header implementation of data structures and some algori
 |Recursive Level order traveral of Tree | [levelOrderTraversalRecursive.cpp](tree_problems/levelOrderTraversalRecursive.cpp), [level_order_tree_traversal_recursive.py](tree_problems/level_order_tree_traversal_recursive.py)|
 |ZigZag Traversal of Tree | [zigZagTraversal.cpp](tree_problems/zigZagTraversal.cpp), [zig_zag_traversal.py](tree_problems/zig_zag_traversal.py)|
 |Predecessor and Successor of a given node in Binary Search Tree | [predecessorSuccessor.cpp](tree_problems/predecessorSuccessor.cpp)|
-|Given values of two nodes in a Binary Search Tree, find the Lowest Common Ancestor (LCA). Assume that both the values exist in the tree.| [lowest-common-ancestor.cpp](tree_problems/lowest-common-ancestor.cpp)|
+|Given values of two nodes in a Binary Search Tree, find the Lowest Common Ancestor (LCA). Assume that both the values exist in the tree.| [lowest-common-ancestor.cpp](tree_problems/lowest-common-ancestor.cpp), [lowest_common_ancestor.py](tree_problems/lowest_common_ancestor.py)|
 |Given a binary tree (unlike binary search tree), find the Lowest Common Ancestor (LCA).|[lowest-common-ancestor-binary-tree.cpp](tree_problems/lowest-common-ancestor-binary-tree.cpp)|
 |Given a binary tree, print out all of its root-to-leaf paths one per line.| [printAllRootToLeafPath.cpp](tree_problems/printAllRootToLeafPath.cpp)
 |Determine if a tree is sum tree. A SumTree is a Binary Tree where the value of a node is equal to sum of the nodes present in its left subtree and right subtree. An empty tree is SumTree and sum of an empty tree can be considered as 0. A leaf node is also considered as SumTree.| [sumTree.cpp](tree_problems/sumTree.cpp)|

tree_problems/lowest_common_ancestor.py

@@ -0,0 +1,63 @@
+"""
+ Given a binary search tree, determine the lowest common ancestor of two given nodes with data
+ key1 and key2. Assumption is key1 and key2 exists in tree
+ Example
+           20
+       /        \
+       8        22
+   /      \
+   4        12
+         /     \
+       10     14
+In the above tree, LCA of 10 and 14 is 12
+similarly 4 and 22 will have LCA 20
+"""
+
+class Node:
+    def __init__(self, data):
+        """Binary Search Tree Node representation"""
+        self.data = data
+        self.left = None
+        self.right = None
+
+
+def LCA(root, key1, key2):
+    if root is None:
+        return None
+
+    if root.data > key1 and root.data > key2:
+        return LCA(root.left, key1, key2)
+
+    elif root.data < key1 and root.data < key2:
+        return LCA(root.right, key1, key2)
+
+    return root
+
+def inorder(root):
+    if root is None:
+        return
+    inorder(root.left)
+    print(root.data, end =' ')
+    inorder(root.right)
+
+
+
+if __name__ == "__main__":
+    root = Node(20)
+    root.right = Node(22)
+    root.left = Node(8)
+    root.left.left = Node(4)
+    root.left.right= Node(12)
+    root.left.right.right = Node(14)
+    root.left.right.left = Node(10)
+    print("Inorder traversal of the tree:")
+    inorder(root);
+    print()
+    print("LCA of nodes with data 10 and 14 is :")
+    print(LCA(root, 14, 10).data);
+    print("LCA of nodes with data 14 and 8 is :")
+    print(LCA(root, 14, 8).data);
+    print("LCA of root with data 4 and 22 is :")
+    print(LCA(root, 4, 22).data);
+    print("LCA of root with data 14 and 10 is :")
+    print(LCA(root, 10, 14).data);