SR-Sunny-Raj#915 Delete Node in a BST

27. LeetCode Problems/450. Delete Node in a BST.cpp

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+/*
+
+Problem Link - https://leetcode.com/problems/delete-node-in-a-bst/
+
+Problem Statement - Given a root node reference of a BST and a key, delete the node with the given key in the BST. Return the root node reference (possibly updated) of the BST.
+
+Basically, the deletion can be divided into two stages:
+
+* Search for a node to remove.
+* If the node is found, delete the node.
+
+
+Example
+
+Input: root = [5,3,6,2,4,null,7], key = 3
+Output: [5,4,6,2,null,null,7]
+Explanation: Given key to delete is 3. So we find the node with value 3 and delete it.
+One valid answer is [5,4,6,2,null,null,7], shown in the above BST.
+Please notice that another valid answer is [5,2,6,null,4,null,7] and it's also accepted.
+
+*/
+
+
+class Solution 
+{
+public:
+
+    // To find the minimum value node in the right sub-tree
+    TreeNode*  minValueNode(TreeNode* node)
+    {
+        TreeNode* cur=node->right;
+        while(cur->left)
+            cur=cur->left;
+
+        return cur;
+    }
+
+    TreeNode* deleteNode(TreeNode* root, int key) 
+    {
+        if(root==NULL)
+            return NULL;
+
+        //if key is greater, then check in right sub-tree
+        if(root->val<key)
+            root->right=deleteNode(root->right,key);
+
+         //if key is smaller, then check in left sub-tree
+        else if(root->val>key)
+            root->left=deleteNode(root->left,key);
+
+        else
+        {
+            // if left or right sub-tree is not present, simply delete the node
+
+            if(root->right==NULL)
+            {
+                TreeNode* temp=root->left;
+                delete(root);
+                return temp;
+            }
+             else if(root->left==NULL)
+            {
+                TreeNode* temp=root->right;
+                delete(root);
+                return temp;
+            }
+
+            // if both sub-trees are present then
+            else
+            {
+                //find minimum value in right subtree and swap it with root
+                TreeNode* temp=minValueNode(root);
+                swap(temp->val,root->val);
+                root->right=deleteNode(root->right,key);
+            }
+
+
+        }
+
+            return root;
+
+    }
+
+};