[C] Challenge 11 (Unreviewed)

challenge_11/c/karanchawla/README.md

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+```
+Karan Chawla
+Challenge 11
+```
+
+This one was a bit tricky to solve but once you think of all the cases, shouldn't be very difficult. 
+The problem can be broken down into 3 cases:
+- 1. If the node to be deleted is a leaf node - in which case you just delete the node.
+- 2. If the node to be deleted has one child - in which case you copy the child to the node and delete the child. 
+- 3. If the node to be deleted has two children - find the successor in right subtree - copy it to the node and delete the successor node.
+
+This is the high level picture - but the implementation may be riddled with more segmentation faults than you'd like, stick with it. You'll get it sooner or later. 
+
+

challenge_11/c/karanchawla/challenge_11.c

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+//Karan Chawla
+//Challenge 11
+
+#include <stdio.h>
+#include <stdlib.h> 
+
+typedef struct node
+{
+	int data;
+	struct node* left, *right;
+}Node;
+
+Node* newNode(int data)
+{
+	Node* node = (Node*)malloc(sizeof(Node));
+
+	node->data = data;
+	node->left = NULL;
+	node->right = NULL;
+
+	return node;
+}
+
+Node* insert(Node* node, int data)
+{
+	if(node==NULL) return newNode(data);
+
+	if(data>node->data)
+	{
+		node->right = insert(node->right,data);
+	}
+	else 
+	{
+		node->left = insert(node->left,data);
+	}
+	return node;
+}
+
+void preOrder(Node* node)
+{
+	if(node==NULL)
+		return;
+
+	printf("%d\n",node->data);
+
+	preOrder(node->left);
+	preOrder(node->right);
+
+	return;
+}
+
+Node* findSmallest(Node* node)
+{
+	while(node->left!=NULL)
+	{
+		node = node->left;
+	}
+
+	return node;
+}
+
+Node* findLargest(Node* node)
+{
+	while(node->right!=NULL)
+	{
+		node = node->right;
+	}
+
+	return node;
+}
+
+/*
+3 caes for node deletion from BST:
+1. Node to be deleted is leaf.
+2. Node to be deleted has one child. 
+3. Node to be deleted has two children.
+*/
+Node* deleteNode(Node* node, int key)
+{
+	//base case
+	if(node==NULL)
+		return node;
+
+	//search in right subtree
+	if(key>node->data)
+	{
+		deleteNode(node->right,key);
+
+	}
+	//search in left sub tree
+	else if(key<node->data)
+	{
+		deleteNode(node->left,key);
+	}
+	//if key is equal to node->data
+	else 
+	{
+		//has only right child - copy the child to the node
+		//and delete node
+		if(node->left==NULL)
+		{
+			Node* tempNode = node->right;
+			free(node);
+			return tempNode;
+		}
+		if(node->right==NULL)
+		{
+			Node* tempNode = node->left;
+			free(node);
+			return tempNode;
+		}
+		//has two children
+		//find the successor using findsmallest in right subtree
+		//copy it to the node and delete the successor node. 
+		else
+		{
+			Node* tempNode = findSmallest(node->right);
+			node->data = tempNode->data;
+			node->right = deleteNode(node->right,tempNode->data);
+		}
+	}
+
+	return node;
+}
+
+//driver function
+int main(void)
+{
+	//Example 1
+	/*
+	struct node *root = NULL;
+    root = insert(root, 1);
+    root = insert(root, 2);
+    root = insert(root, 3);
+    root = insert(root, 4);
+    root = insert(root, 7);
+    root = insert(root, 6);
+    root = insert(root, 8);
+    */
+
+    //number of nodes input
+    printf("Enter the numer of nodes you want in the BST:\n");
+    int t;
+    scanf("%d",&t);
+
+    //node data input
+    printf("Now enter the node data values\n");
+
+    //Tree initialization
+    Node* root = NULL;
+
+    //data values from user 
+    while(t--)
+    {
+    	int key;
+    	scanf("%d",&key)
+    	root = insert(root,key);
+    }
+
+    printf("Before deletion your BST looks like:\n");
+
+    preOrder(root);
+    deleteNode(root,70);
+
+    printf("After deletino the BST looks like\n");
+    preOrder(root);
+
+    return 0;
+}