From e22c6e9463cbccc77da3b54ec311757fddb96e41 Mon Sep 17 00:00:00 2001
From: Dhananjay <dhananjay.shettigar@juspay.in>
Date: Mon, 4 Oct 2021 22:02:38 +0530
Subject: [PATCH 1/4] Added simple functions to BinaryTree Structure

---
 src/BinaryTree/BinaryTree.hs | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/src/BinaryTree/BinaryTree.hs b/src/BinaryTree/BinaryTree.hs
index f703217..c84c662 100644
--- a/src/BinaryTree/BinaryTree.hs
+++ b/src/BinaryTree/BinaryTree.hs
@@ -2,7 +2,7 @@ module BinaryTree.BinaryTree where
 
 import qualified Data.List as L
 
-data BTree a = Empty | Node a (BTree a) (BTree a) deriving (Show)
+data BTree a = Empty | Node a (BTree a) (BTree a) deriving (Show, Eq)
 data Side = LeftSide | RightSide deriving (Eq, Show)
 
 -- Get subtree on specified side
@@ -68,4 +68,28 @@ numNodes t = length $ bfsList t
 -- Pretty Print a Binary Tree
 simplePrint :: (Show a) => BTree a -> String
 simplePrint Empty = ""
-simplePrint t = (nodeShow t) ++ " " ++ (simplePrint $ getLeftTree t) ++ (simplePrint $ getRightTree t)
\ No newline at end of file
+simplePrint t = (nodeShow t) ++ " " ++ (simplePrint $ getLeftTree t) ++ (simplePrint $ getRightTree t)
+
+-- Find count of element occurrence in binary tree
+elementCountInTree :: (Ord a, Eq a) => BTree a -> a -> Int
+elementCountInTree Empty _ = 0
+elementCountInTree (Node x l r) ele =
+    (if ele == x then 1 else 0) + 
+    elementCountInTree l ele    +
+    elementCountInTree r ele
+
+-- Find whether tree is symmetric at root
+-- Uses Haskell Eq instance to compare BTree datatype
+isSymmetric :: (Eq a) => BTree a -> Bool
+isSymmetric (Node _ l r) = l == r
+
+-- Get sum of all elements in tree
+sumTree :: (Ord a, Eq a) => BTree a -> Int
+sumTree (Node x l r) = x + sumTree l + sumTree r 
+
+-- Get an array of leaf nodes in a binary tree
+getLeafNodes :: (Show a) => BTree a -> [a]
+getLeafNodes Empty = []
+getLeafNodes (Node x l r)
+    | l == Empty && r == Empty = [x]
+    | otherwise = getLeafNodes l ++ getLeafNodes r
\ No newline at end of file

From 0084a0913010bab816ed3335cc45e126512d769e Mon Sep 17 00:00:00 2001
From: Dhananjay <dhananjay.shettigar@juspay.in>
Date: Mon, 4 Oct 2021 22:02:58 +0530
Subject: [PATCH 2/4] Added simple functions to BinarySearchTree Structure

---
 src/BinaryTree/BinarySearchTree.hs | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/src/BinaryTree/BinarySearchTree.hs b/src/BinaryTree/BinarySearchTree.hs
index f955921..ec99c25 100644
--- a/src/BinaryTree/BinarySearchTree.hs
+++ b/src/BinaryTree/BinarySearchTree.hs
@@ -14,6 +14,16 @@ inorderWalk :: (Eq a, Ord a) => BTree a -> [a]
 inorderWalk Empty = []
 inorderWalk (Node x l r) = (inorderWalk l) ++ [x] ++ (inorderWalk r)
 
+-- Perform preorder walk of the binary search tree
+preorderWalk :: (Eq a, Ord a) => BTree a -> [a]
+preorderWalk Empty = []
+preorderWalk (Node x l r) = [x] ++ preorderWalk l ++ preorderWalk r
+
+-- Perform postorder walk of the binary search tree
+postorderWalk :: (Eq a, Ord a) => BTree a -> [a]
+postorderWalk Empty = []
+postorderWalk (Node x l r) = preorderWalk l ++ preorderWalk r ++ [x]
+
 -- Function to insert a value into the tree. Returns the new tree.
 -- Cormen, Thomas H., et al. Introduction to algorithms.  pg. 294, MIT press, 2009.
 bstInsert :: (Eq a, Ord a) => BTree a -> a -> BTree a
@@ -54,4 +64,12 @@ isBST Empty = True
 isBST (Node x Empty Empty) = True
 isBST (Node x Empty r) = (x < (nkey r)) && (isBST r) where nkey = (\(Node n ll rr) -> n)
 isBST (Node x l Empty) = (x >= (nkey l)) && (isBST l) where nkey = (\(Node n ll rr) -> n)
-isBST (Node x l r) = (x >= (nkey l)) && (x < (nkey r)) && (isBST l) && (isBST r) where nkey = (\(Node n ll rr) -> n)
\ No newline at end of file
+isBST (Node x l r) = (x >= (nkey l)) && (x < (nkey r)) && (isBST l) && (isBST r) where nkey = (\(Node n ll rr) -> n)
+
+isElementInBST :: (Ord a, Eq a) => BTree a -> a -> Bool
+isElementInBST Empty _ = False
+isElementInBST (Node x l r) ele = 
+    x == ele ||
+    if x < ele 
+        then isElementInBST r ele
+        else isElementInBST l ele

From abc697f5beda27e860ca75d2deb106e42a5bc50d Mon Sep 17 00:00:00 2001
From: Dhananjay <dhananjay.shettigar@juspay.in>
Date: Mon, 4 Oct 2021 22:40:17 +0530
Subject: [PATCH 3/4] Minor fix

---
 src/BinaryTree/BinaryTree.hs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/BinaryTree/BinaryTree.hs b/src/BinaryTree/BinaryTree.hs
index c84c662..6ab6707 100644
--- a/src/BinaryTree/BinaryTree.hs
+++ b/src/BinaryTree/BinaryTree.hs
@@ -84,11 +84,12 @@ isSymmetric :: (Eq a) => BTree a -> Bool
 isSymmetric (Node _ l r) = l == r
 
 -- Get sum of all elements in tree
-sumTree :: (Ord a, Eq a) => BTree a -> Int
+sumTree :: BTree Int -> Int
+sumTree Empty = 0
 sumTree (Node x l r) = x + sumTree l + sumTree r 
 
 -- Get an array of leaf nodes in a binary tree
-getLeafNodes :: (Show a) => BTree a -> [a]
+getLeafNodes :: (Eq a, Show a) => BTree a -> [a]
 getLeafNodes Empty = []
 getLeafNodes (Node x l r)
     | l == Empty && r == Empty = [x]

From d9aa5f29e4e45d4766e22e7eeb6552adb1c92897 Mon Sep 17 00:00:00 2001
From: Dhananjay <dhananjay.shettigar@juspay.in>
Date: Mon, 4 Oct 2021 22:45:28 +0530
Subject: [PATCH 4/4] Minor fix

---
 src/BinaryTree/BinaryTree.hs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/BinaryTree/BinaryTree.hs b/src/BinaryTree/BinaryTree.hs
index 6ab6707..86372c8 100644
--- a/src/BinaryTree/BinaryTree.hs
+++ b/src/BinaryTree/BinaryTree.hs
@@ -81,6 +81,7 @@ elementCountInTree (Node x l r) ele =
 -- Find whether tree is symmetric at root
 -- Uses Haskell Eq instance to compare BTree datatype
 isSymmetric :: (Eq a) => BTree a -> Bool
+isSymmetric Empty = True
 isSymmetric (Node _ l r) = l == r
 
 -- Get sum of all elements in tree