1 CSE 2341 Object Oriented Programming with C++ Note Set #21

2 Overview Recursive linked list ops Binary Trees

3 Recursion w/ LL Recursion can be used to traverse a linked list Any recursive solution has an iterative counterpart –recursive is sometime more elegant though 2 functions : –countNodes(ListNode*); –showReverse(ListNode*);

4 Counting Nodes in a List int NumberList::numNodes() { return countNodes(head); } int NumberList::countNodes(ListNode* nodePtr) { if(nodePtr != NULL) return 1 + countNodes(nodePtr->next); else return 0; } Must provide public member function. Recursive function must start at head, but head can’t be passed in from outside the class.

5 Counting Nodes in a List int NumberList::countNodes(ListNode* nodePtr) { if(nodePtr != NULL) return 1 + countNodes(nodePtr->next); else return 0; } 534 Head Null

6 Counting Nodes in a List int NumberList::countNodes(3000) { if(nodePtr != NULL) return 1 + countNodes(3008); else return 0; } 534 Head Null stack

7 Counting Nodes in a List int NumberList::countNodes(3000) { if(nodePtr != NULL) return 1 + countNodes(3008); else return 0; } 534 Head Null int NumberList::countNodes(3008) { if(nodePtr != NULL) return 1 + countNodes(3016); else return 0; } stack

8 Counting Nodes in a List int NumberList::countNodes(3000) { if(nodePtr != NULL) return 1 + countNodes(3008); else return 0; } 534 Head Null int NumberList::countNodes(3008) { if(nodePtr != NULL) return 1 + countNodes(3016); else return 0; } int NumberList::countNodes(3016) { if(nodePtr != NULL) return 1 + countNodes(NULL); else return 0; } stack

9 Counting Nodes in a List int NumberList::countNodes(3000) { if(nodePtr != NULL) return 1 + countNodes(3008); else return 0; } 534 Head Null int NumberList::countNodes(3008) { if(nodePtr != NULL) return 1 + countNodes(3016); else return 0; } int NumberList::countNodes(3016) { if(nodePtr != NULL) return 1 + countNodes(NULL); else return 0; } int NumberList::countNodes(NULL) { if(nodePtr != NULL) return 1 + countNodes(nodePtr->next); else return 0; } stack

10 Counting Nodes in a List int NumberList::countNodes(3000) { if(nodePtr != NULL) return 1 + countNodes(3008); else return 0; } 534 Head Null int NumberList::countNodes(3008) { if(nodePtr != NULL) return 1 + countNodes(3016); else return 0; } int NumberList::countNodes(3016) { if(nodePtr != NULL) return 1 + 0; else return 0; } stack

11 Counting Nodes in a List int NumberList::countNodes(3000) { if(nodePtr != NULL) return 1 + countNodes(3008); else return 0; } 534 Head Null int NumberList::countNodes(3008) { if(nodePtr != NULL) return 1 + 1; else return 0; } stack

12 Counting Nodes in a List int NumberList::countNodes(3000) { if(nodePtr != NULL) return 1 + 2; else return 0; } 534 Head Null stack finally returns 3 to numNodes

13 Displaying Nodes in Reverse Order int NumberList::displayBackwards() { return showReverse(head); } int NumberList::showReverse(ListNode* nodePtr) { if(nodePtr != NULL) { showReverse(nodePtr->next); cout value << “ “; } Must provide public member function. Recursive function must start at head, but head can’t be passed in from outside the class.

14 Counting Nodes in a List void NumberList::showReverse(ListNode* nodePtr) { if(nodePtr != NULL) { showReverse(nodePtr->next); cout value << “ “; } 534 Head Null

15 Counting Nodes in a List void NumberList::showReverse(3000) { if(nodePtr != NULL) { showReverse(3008); cout value << “ “; } 534 Head Null

16 Counting Nodes in a List void NumberList::showReverse(3000) { if(nodePtr != NULL) { showReverse(3008); cout value << “ “; } 534 Head Null void NumberList::showReverse(3008) { if(nodePtr != NULL) { showReverse(3016); cout value << “ “; }

17 Counting Nodes in a List void NumberList::showReverse(3000) { if(nodePtr != NULL) { showReverse(3008); cout value << “ “; } 534 Head Null void NumberList::showReverse(3008) { if(nodePtr != NULL) { showReverse(3016); cout value << “ “; } void NumberList::showReverse(3016) { if(nodePtr != NULL) { showReverse(NULL); cout value << “ “; }

18 Counting Nodes in a List void NumberList::showReverse(3000) { if(nodePtr != NULL) { showReverse(3008); cout value << “ “; } 534 Head Null void NumberList::showReverse(3008) { if(nodePtr != NULL) { showReverse(3016); cout value << “ “; } void NumberList::showReverse(3016) { if(nodePtr != NULL) { showReverse(NULL); cout value << “ “; } void NumberList::showReverse(NULL) { if(nodePtr != NULL) { showReverse(NULL); cout value << “ “; }

19 Counting Nodes in a List void NumberList::showReverse(3000) { if(nodePtr != NULL) { showReverse(3008); cout value << “ “; } 534 Head Null void NumberList::showReverse(3008) { if(nodePtr != NULL) { showReverse(3016); cout value << “ “; } void NumberList::showReverse(3016) { if(nodePtr != NULL) { showReverse(NULL); cout value << “ “; }

20 Counting Nodes in a List void NumberList::showReverse(3000) { if(nodePtr != NULL) { showReverse(3008); cout value << “ “; } 534 Head Null void NumberList::showReverse(3008) { if(nodePtr != NULL) { showReverse(3016); cout value << “ “; }

21 Counting Nodes in a List void NumberList::showReverse(3000) { if(nodePtr != NULL) { showReverse(3008); cout value << “ “; } 534 Head Null

22 Binary Trees

23 Binary Tree –non linear linked structure –each node may point to 2 other nodes –every node has exactly 1 predecessor tree pointer

24 Binary Tree tree pointer p f a t z null

25 Binary Tree Terminology tree pointer p f a t z null Left Subtree Leaf Node Root Node

26 Basis: TreeNode struct TreeNode { int value; TreeNode* left; TreeNOde* right; };

27 IntBinaryTree Class class IntBinaryTree { private: struct TreeNode { int value; TreeNode *left; TreeNode *right; }; TreeNode *root; void insert(TreeNode *&, TreeNode *&); void destroySubTree(TreeNode *); void deleteNode(int, TreeNode *&); void makeDeletion(TreeNode *&); void displayInOrder(TreeNode *); void displayPreOrder(TreeNode *); void displayPostOrder(TreeNode *);

28 IntBinaryTree Class Continued public: IntBinaryTree()// Constructor { root = NULL; } ~IntBinaryTree()// Destructor { destroySubTree(root); } void insertNode(int); bool searchNode(int); void remove(int); void displayInOrder() {displayInOrder(root); } void displayPreOrder() {displayPreOrder(root); } void displayPostOrder() {displayPostOrder(root); } };

29 IntBinaryTree Class INSERT void IntBinaryTree::insertNode(int num) { TreeNode *newNode;// Pointer to a new node. // Create a new node and store num in it. newNode = new TreeNode; newNode->value = num; newNode->left = newNode->right = NULL; // Insert the node. insert(root, newNode); } Public member function to insert an integer. Calls the private member function insert.

30 IntBinaryTree Class INSERT void IntBinaryTree::insert(TreeNode*& nodePtr, TreeNode*& newNode) { if (nodePtr == NULL) nodePtr = newNode; // Insert the node. else if (newNode->value value) insert(nodePtr->left, newNode);//Search left branch else insert(nodePtr->right, newNode);//Search right branch } Private member function to insert an integer.

31 Binary Trees Next Week –Traversals in order pre order post order –Searching –Destroying –Deleting one node

32 Fini ?