Merge pull request #622 from SegFault03/main

Delete nodes in a binary tree

Trees/delete_nodes_BST.cpp

@@ -0,0 +1,139 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+class Tree
+{
+public:
+
+    int val;
+    Tree *left;
+    Tree *right;
+
+public:
+
+    //class constructor called when any object or pointer is created without any parameter.
+    Tree()                          
+    {
+        val=0;
+        left=nullptr;
+        right=nullptr;
+    }
+
+     //class constructor called when an object or pointer is called while passing an argument (val). 
+    Tree(int val)                  
+    {
+        this->val=val;
+        this->left=nullptr;
+        this->right=nullptr;
+    }
+
+    //builds a Binary Tree taking (int) value as an argument and returns the root to the tree built. 
+    Tree* buildTree(int val)
+    {
+        if(this==nullptr)
+        {
+            Tree *temp = new Tree(val);
+            return temp;
+        }
+        else
+        {
+            Tree *temp=nullptr;
+            if(this->val>val)
+            {
+                temp=this->left->buildTree(val);
+                this->left=temp;
+            }
+            else
+            {
+                temp=this->right->buildTree(val);
+                this->right=temp;
+            }
+            return this;
+        }
+    }
+
+    //RECURSIVE DFS PREORDER
+    void preOrder()     
+    {
+        if(this!=nullptr)
+        {
+            cout<<this->val<<",";
+            this->left->preOrder();
+            this->right->preOrder();
+        }
+    }
+};
+
+Tree* deleteNode(Tree *root, int val)
+{
+    if(root==nullptr)
+    return nullptr;
+    else
+    {
+        if(root->val>val)
+        root->left=deleteNode(root->left,val);
+        else if(root->val<val)
+        root->right=deleteNode(root->right,val);
+        else
+        {
+            if(root->left!=nullptr)
+            {
+                Tree *temp=root->left;
+                Tree *trav=temp->right;
+                if(trav==nullptr)
+                {
+                    temp->right=root->right;
+                    root=temp;
+                }
+                else
+                {
+                    while(trav->right!=nullptr)
+                    {
+                        temp=trav;
+                        trav=trav->right;
+                    }
+                    temp->right=trav->left;
+                    root->val=trav->val;
+                    trav->left=NULL;
+                }
+            }
+            else if(root->right!=nullptr)
+            {
+                Tree *temp=root->right;
+                Tree *trav=temp->left;
+                if(trav==nullptr)
+                {
+                    temp->left=root->left;
+                    root=temp;
+                }
+                else
+                {
+                    while(trav->left!=nullptr)
+                    {
+                        temp=trav;
+                        trav=trav->left;
+                    }
+                    temp->left=trav->right;
+                    root->val=trav->val;
+                    trav->right=NULL;
+                }
+            }
+            else
+            root=nullptr;
+        }
+        return root;
+    }
+}
+
+int main()
+{
+    vector<int>test={8,5,3,6,11,10,9,12};
+    Tree *root=nullptr;
+    for(int i:test)
+    root=root->buildTree(i);
+    cout<<"The tree:  ";
+    root->preOrder();
+    root=deleteNode(root,6);
+    cout<<"\nThe tree after deletion:  ";
+    root->preOrder();
+}