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POBinary Search Tree C implementation
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copied!<p>I recently wrote a fairly simple piece of code attempting to implement a Binary Search Tree in C with insertion, search, deletion and display operations. Unfortunately, the code does not seem to work.</p> <pre><code>#include <stdio.h> #include <stdlib.h> struct TreeNode { int data; struct TreeNode *leftChildNode; struct TreeNode *rightChildNode; }; typedef struct TreeNode node; node *rootNode = NULL; void insertNode(int i, node *n) { if(n == NULL) { n = (node*)malloc(sizeof(node)); n->leftChildNode = NULL; n->rightChildNode = NULL; n->data = i; } else if(n->data == i) printf("\nThis value already exists in the tree!"); else if(i > n->data) insertNode(i, n->rightChildNode); else insertNode(i, n->leftChildNode); } void searchNode(int i, node *n) { if(n == NULL) printf("\nValue does not exist in tree!"); else if(n->data == i) printf("\nValue found!"); else if(i > n->data) searchNode(i, n->rightChildNode); else searchNode(i, n->leftChildNode); } void deleteNode(int i, node *n) { if(n == NULL) printf("\nValue does not exist in tree!"); else if(n->data == i) { if(n->leftChildNode == NULL) n = n->rightChildNode; else if(n->rightChildNode == NULL) n = n->leftChildNode; else { node *temp = n->rightChildNode; while(temp->leftChildNode != NULL) temp = temp->leftChildNode; n = temp; } } else if(i > n->data) deleteNode(i, n->rightChildNode); else deleteNode(i, n->leftChildNode); } void displayPreOrder(node *n) { if(n != NULL) { printf("%d ", n->data); displayPreOrder(n->leftChildNode); displayPreOrder(n->rightChildNode); } } void displayPostOrder(node *n) { if(n != NULL) { displayPostOrder(n->leftChildNode); displayPostOrder(n->rightChildNode); printf("%d ", n->data); } } void displayInOrder(node *n) { if(n != NULL) { displayInOrder(n->leftChildNode); printf("%d ", n->data); displayInOrder(n->rightChildNode); } } int main(void) { int ch, num, num1; do { printf("\nSelect a choice from the menu below."); printf("\n1. Insert a node."); printf("\n2. Search for a node."); printf("\n3. Delete a node."); printf("\n4. Display the Binary Search Tree."); printf("\nChoice: "); scanf("%d", &ch); switch(ch) { case 1: printf("\nEnter an element: "); scanf("%d", &num); //printf("YESYES"); insertNode(num, rootNode); break; case 2: printf("\nEnter the element to be searched for: "); scanf("%d", &num); searchNode(num, rootNode); break; case 3: printf("\nEnter the element to be deleted: "); scanf("%d", &num); deleteNode(num, rootNode); break; case 4: printf("\nSelect an order for the elements to be display in."); printf("\n1. Pre-order."); printf("\n2. Post-order."); printf("\n3. In-order."); printf("\nChoice: "); scanf("%d", &num1); switch(num1) { case 1: printf("\nPre-order Display: "); displayPreOrder(rootNode); break; case 2: printf("\nPost-order Display: "); displayPostOrder(rootNode); break; case 3: printf("\nIn-order Display: "); displayInOrder(rootNode); break; default: exit(0); } break; default: exit(0); } //printf("%d", rootNode->data); printf("\nIf you want to return to the menu, press 1."); printf("\nChoice: "); scanf("%d", &num); } while(num == 1); return 0; } </code></pre> <p>In fact, notice the commented line <code>printf("%d", rootNode->data);</code> just before the <code>do-while</code> block in <code>main()</code> ends. If I uncomment this line, compile the program and run it, the program throws a segmentation fault. Could anyone tell me why this error is occurring and why the code as a whole isn't running? Thanks in advance.</p>

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