From ce53fee92fd6def93e81150e14a9445a492ec79b Mon Sep 17 00:00:00 2001
From: Madhur Panwar <39766613+mdrpanwar@users.noreply.github.com>
Date: Wed, 20 Oct 2021 21:08:21 +0530
Subject: [PATCH] Add Implementation of Tree Sort and Generic Type BST (#2638)

---
 DataStructures/Trees/BSTRecursive.java        |   2 +-
 DataStructures/Trees/BSTRecursiveGeneric.java | 296 ++++++++++++++++++
 Sorts/TreeSort.java                           | 113 +++++++
 3 files changed, 410 insertions(+), 1 deletion(-)
 create mode 100644 DataStructures/Trees/BSTRecursiveGeneric.java
 create mode 100644 Sorts/TreeSort.java

diff --git a/DataStructures/Trees/BSTRecursive.java b/DataStructures/Trees/BSTRecursive.java
index b6536a7b..3802ceb4 100644
--- a/DataStructures/Trees/BSTRecursive.java
+++ b/DataStructures/Trees/BSTRecursive.java
@@ -26,7 +26,7 @@ public class BSTRecursive {
 
   /** main function for tests */
   public static void main(String[] args) {
-    BSTIterative tree = new BSTIterative();
+    BSTRecursive tree = new BSTRecursive();
     tree.add(5);
     tree.add(10);
     tree.add(9);
diff --git a/DataStructures/Trees/BSTRecursiveGeneric.java b/DataStructures/Trees/BSTRecursiveGeneric.java
new file mode 100644
index 00000000..a3b117a6
--- /dev/null
+++ b/DataStructures/Trees/BSTRecursiveGeneric.java
@@ -0,0 +1,296 @@
+package DataStructures.Trees;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * <h1>Binary Search Tree (Recursive) Generic Type Implementation</h1>
+ *
+ * <p>
+ * A recursive implementation of generic type BST.
+ *
+ * Reference: https://en.wikipedia.org/wiki/Binary_search_tree
+ * </p>
+ *
+ * @author [Madhur Panwar](https://github.com/mdrpanwar)
+ */
+public class BSTRecursiveGeneric<T extends Comparable<T>> {
+  /** only data member is root of BST */
+  private Node<T> root;
+
+  /** Constructor use to initialize node as null */
+  public BSTRecursiveGeneric() {
+    root = null;
+  }
+
+  /** main function for testing */
+  public static void main(String[] args) {
+    System.out.println("Testing for integer data...");
+    // Integer
+    DataStructures.Trees.BSTRecursiveGeneric<Integer> integerTree = new DataStructures.Trees.BSTRecursiveGeneric<Integer>();
+
+    integerTree.add(5);
+    integerTree.add(10);
+    integerTree.add(9);
+    assert !integerTree.find(4) : "4 is not yet present in BST";
+    assert integerTree.find(10) : "10 should be present in BST";
+    integerTree.remove(9);
+    assert !integerTree.find(9) : "9 was just deleted from BST";
+    integerTree.remove(1);
+    assert !integerTree.find(1) : "Since 1 was not present so find deleting would do no change";
+    integerTree.add(20);
+    integerTree.add(70);
+    assert integerTree.find(70) : "70 was inserted but not found";
+    /*
+     Will print in following order
+     5 10 20 70
+    */
+    integerTree.inorder();
+    System.out.println();
+    System.out.println("Testing for string data...");
+    // String
+    DataStructures.Trees.BSTRecursiveGeneric<String> stringTree = new DataStructures.Trees.BSTRecursiveGeneric<String>();
+
+    stringTree.add("banana");
+    stringTree.add("pineapple");
+    stringTree.add("date");
+    assert !stringTree.find("girl") : "girl is not yet present in BST";
+    assert stringTree.find("pineapple") : "10 should be present in BST";
+    stringTree.remove("date");
+    assert !stringTree.find("date") : "date was just deleted from BST";
+    stringTree.remove("boy");
+    assert !stringTree.find("boy") : "Since boy was not present so deleting would do no change";
+    stringTree.add("india");
+    stringTree.add("hills");
+    assert stringTree.find("hills") : "hills was inserted but not found";
+    /*
+     Will print in following order
+     banana hills india pineapple
+    */
+    stringTree.inorder();
+
+  }
+
+  /**
+   * Recursive method to delete a data if present in BST.
+   *
+   * @param node the node under which to (recursively) search for data
+   * @param data the value to be deleted
+   * @return Node the updated value of root parameter after delete operation
+   */
+  private Node<T> delete(Node<T> node, T data) {
+    if (node == null) {
+      System.out.println("No such data present in BST.");
+    } else if (node.data.compareTo(data) > 0) {
+      node.left = delete(node.left, data);
+    } else if (node.data.compareTo(data) < 0) {
+      node.right = delete(node.right, data);
+    } else {
+      if (node.right == null && node.left == null) { // If it is leaf node
+        node = null;
+      } else if (node.left == null) { // If only right node is present
+        Node<T> temp = node.right;
+        node.right = null;
+        node = temp;
+      } else if (node.right == null) { // Only left node is present
+        Node<T> temp = node.left;
+        node.left = null;
+        node = temp;
+      } else { // both child are present
+        Node<T> temp = node.right;
+        // Find leftmost child of right subtree
+        while (temp.left != null) {
+          temp = temp.left;
+        }
+        node.data = temp.data;
+        node.right = delete(node.right, temp.data);
+      }
+    }
+    return node;
+  }
+
+  /**
+   * Recursive insertion of value in BST.
+   *
+   * @param node to check if the data can be inserted in current node or its subtree
+   * @param data the value to be inserted
+   * @return the modified value of the root parameter after insertion
+   */
+  private Node<T> insert(Node<T> node, T data) {
+    if (node == null) {
+      node = new Node<>(data);
+    } else if (node.data.compareTo(data) > 0) {
+      node.left = insert(node.left, data);
+    } else if (node.data.compareTo(data) < 0) {
+      node.right = insert(node.right, data);
+    }
+    return node;
+  }
+
+  /**
+   * Recursively print Preorder traversal of the BST
+   *
+   * @param node the root node
+   */
+  private void preOrder(Node<T> node) {
+    if (node == null) {
+      return;
+    }
+    System.out.print(node.data + " ");
+    if (node.left != null) {
+      preOrder(node.left);
+    }
+    if (node.right != null) {
+      preOrder(node.right);
+    }
+  }
+
+  /**
+   * Recursively print Postorder traversal of BST.
+   *
+   * @param node the root node
+   */
+  private void postOrder(Node<T> node) {
+    if (node == null) {
+      return;
+    }
+    if (node.left != null) {
+      postOrder(node.left);
+    }
+    if (node.right != null) {
+      postOrder(node.right);
+    }
+    System.out.print(node.data + " ");
+  }
+
+  /**
+   * Recursively print Inorder traversal of BST.
+   *
+   * @param node the root node
+   */
+  private void inOrder(Node<T> node) {
+    if (node == null) {
+      return;
+    }
+    if (node.left != null) {
+      inOrder(node.left);
+    }
+    System.out.print(node.data + " ");
+    if (node.right != null) {
+      inOrder(node.right);
+    }
+  }
+
+  /**
+   * Recursively traverse the tree using inorder traversal
+   * and keep adding elements to argument list.
+   *
+   * @param node the root node
+   * @param sortedList the list to add the srted elements into
+   */
+  private void inOrderSort(Node<T> node, List<T> sortedList) {
+    if (node == null) {
+      return;
+    }
+    if (node.left != null) {
+      inOrderSort(node.left, sortedList);
+    }
+    sortedList.add(node.data);
+    if (node.right != null) {
+      inOrderSort(node.right, sortedList);
+    }
+  }
+
+  /**
+   * Serach recursively if the given value is present in BST or not.
+   *
+   * @param node the node under which to check
+   * @param data the value to be checked
+   * @return boolean if data is present or not
+   */
+  private boolean search(Node<T> node, T data) {
+    if (node == null) {
+      return false;
+    } else if (node.data.compareTo(data) == 0) {
+      return true;
+    } else if (node.data.compareTo(data) > 0) {
+      return search(node.left, data);
+    } else {
+      return search(node.right, data);
+    }
+  }
+
+  /**
+   * add in BST. if the value is not already present it is inserted or else no change takes place.
+   *
+   * @param data the value to be inserted
+   */
+  public void add(T data) {
+    this.root = insert(this.root, data);
+  }
+
+  /**
+   * If data is present in BST delete it else do nothing.
+   *
+   * @param data the value to be removed
+   */
+  public void remove(T data) {
+    this.root = delete(this.root, data);
+  }
+
+  /** To call inorder traversal on tree */
+  public void inorder() {
+    System.out.println("Inorder traversal of this tree is:");
+    inOrder(this.root);
+    System.out.println(); // for next line
+  }
+
+  /** return a sorted list by traversing the tree elements using inorder traversal */
+  public List<T> inorderSort() {
+    List<T> sortedList = new ArrayList<>();
+    inOrderSort(this.root, sortedList);
+    return sortedList;
+  }
+
+  /** To call postorder traversal on tree */
+  public void postorder() {
+    System.out.println("Postorder traversal of this tree is:");
+    postOrder(this.root);
+    System.out.println(); // for next line
+  }
+
+  /** To call preorder traversal on tree. */
+  public void preorder() {
+    System.out.println("Preorder traversal of this tree is:");
+    preOrder(this.root);
+    System.out.println(); // for next line
+  }
+
+  /**
+   * To check if given value is present in tree or not.
+   *
+   * @param data the data to be found for
+   */
+  public boolean find(T data) {
+    if (search(this.root, data)) {
+      System.out.println(data + " is present in given BST.");
+      return true;
+    }
+    System.out.println(data + " not found.");
+    return false;
+  }
+
+  /** The generic Node class used for building binary search tree */
+  private static class Node<T> {
+    T data;
+    Node<T> left;
+    Node<T> right;
+
+    /** Constructor with data as parameter */
+    Node(T d) {
+      data = d;
+      left = null;
+      right = null;
+    }
+  }
+}
diff --git a/Sorts/TreeSort.java b/Sorts/TreeSort.java
new file mode 100644
index 00000000..126625db
--- /dev/null
+++ b/Sorts/TreeSort.java
@@ -0,0 +1,113 @@
+package Sorts;
+
+import static Sorts.SortUtils.print;
+
+import java.util.List;
+
+/**
+ * <h1> Implementation of the Tree Sort algorithm</h1>
+ *
+ * <p>
+ * Tree Sort: A sorting algorithm which constructs a Binary Search Tree
+ * using the unsorted data and then outputs the data by inorder traversal
+ * of the tree.
+ *
+ * Reference: https://en.wikipedia.org/wiki/Tree_sort
+ * </p>
+ *
+ * @author Madhur Panwar (https://github.com/mdrpanwar)
+ */
+public class TreeSort implements SortAlgorithm {
+
+  @Override
+  public <T extends Comparable<T>> T[] sort(T[] unsortedArray) {
+    return doTreeSortArray(unsortedArray);
+  }
+
+  @Override
+  public <T extends Comparable<T>> List<T> sort(List<T> unsortedList) {
+    return doTreeSortList(unsortedList);
+  }
+
+  private <T extends Comparable<T>> T[] doTreeSortArray(T[] unsortedArray) {
+    // create a generic BST tree
+    DataStructures.Trees.BSTRecursiveGeneric<T> tree = new DataStructures.Trees.BSTRecursiveGeneric<T>();
+
+    // add all elements to the tree
+    for(T element: unsortedArray) {
+      tree.add(element);
+    }
+
+    // get the sorted list by inorder traversal of the tree
+    List<T> sortedList = tree.inorderSort();
+
+    // add the elements back to the initial array
+    int i = 0;
+    for(T element: sortedList) {
+      unsortedArray[i++] = element;
+    }
+
+    // return the array
+    return unsortedArray;
+  }
+
+  private <T extends Comparable<T>> List<T> doTreeSortList(List<T> unsortedList) {
+    // create a generic BST tree
+    DataStructures.Trees.BSTRecursiveGeneric<T> tree = new DataStructures.Trees.BSTRecursiveGeneric<T>();
+
+    // add all elements to the tree
+    for(T element: unsortedList) {
+      tree.add(element);
+    }
+
+    // get the sorted list by inorder traversal of the tree and return it
+    return tree.inorderSort();
+  }
+
+  public static void main(String[] args) {
+    TreeSort treeSort = new TreeSort();
+
+    // ==== Integer Array =======
+    System.out.println("Testing for Integer Array....");
+    Integer[] a = { 3, -7, 45, 1, 343, -5, 2, 9 };
+    System.out.print(String.format("%-10s", "unsorted: "));
+    print(a);
+    a = treeSort.sort(a);
+    System.out.print(String.format("%-10s", "sorted: "));
+    print(a);
+    System.out.println();
+
+    // ==== Integer List =======
+    System.out.println("Testing for Integer List....");
+    List<Integer> intList = List.of(3, -7, 45, 1, 343, -5, 2, 9);
+    System.out.print(String.format("%-10s", "unsorted: "));
+    print(intList);
+    intList = treeSort.sort(intList);
+    System.out.print(String.format("%-10s", "sorted: "));
+    print(intList);
+    System.out.println();
+
+
+    // ==== String Array =======
+    System.out.println("Testing for String Array....");
+    String[] b = { "banana", "berry", "orange", "grape", "peach", "cherry", "apple", "pineapple" };
+    System.out.print(String.format("%-10s", "unsorted: "));
+    print(b);
+    b = treeSort.sort(b);
+    System.out.print(String.format("%-10s", "sorted: "));
+    print(b);
+    System.out.println();
+
+    // ==== String List =======
+    System.out.println("Testing for String List....");
+    List<String> stringList = List.of("banana", "berry", "orange", "grape", "peach", "cherry", "apple", "pineapple");
+    System.out.print(String.format("%-10s", "unsorted: "));
+    print(stringList);
+    stringList = treeSort.sort(stringList);
+    System.out.print(String.format("%-10s", "sorted: "));
+    print(stringList);
+
+  }
+
+}
+