Added deletion of node functionality to binary tree in c++

Author: adenashameem

classical_algorithms/c++/binary_tree.cpp

@@ -1,4 +1,5 @@
 #include <iostream> 
+#include<bits/stdc++.h>
 using namespace std; 
 
 struct Node { 
@@ -18,19 +19,123 @@ struct Node {
 		right = NULL; 
 	} 
 }; 
+/*Function which print level order of the given tree*/ 
+void level_order(Node* root)
+{
+   if(root==NULL)
+   { 
+       return;
+   }
+   queue<Node*> q;
+   q.push(root);
+   while(!q.empty())
+   {
+       Node* temp=q.front();
+       cout<<temp->data<<" ";
+       q.pop();
+       if(temp->left!=NULL)
+       {
+           q.push(temp->left);
+       }
+       if(temp->right!=NULL)
+       {
+           q.push(temp->right);
+       }
+   }
+   cout<<endl;
+}
+pair<Node*,int> last_node(Node* root)
+{
+   if(root==NULL)
+   { 
+       return make_pair(root,0);
+   }
+   queue<Node*> q;
+   q.push(root);
+   Node* last_parent=NULL;
+   int last_value;
+   while(!q.empty())
+   {
+       Node* temp=q.front();
+       /*store the parent of last node*/
+       if((temp->left!=NULL)&&(temp->right!=NULL))//if left and right sub tree are present;
+       {
+           if(temp->left->left==NULL&&temp->left->right==NULL&&temp->right->left==NULL&&temp->right->right==NULL)
+           {
+              last_parent=temp;
+           }
+       }
+       if(temp->left!=NULL)//if left subtree only present;
+       {
+           if(temp->left->left==NULL&&temp->left->right==NULL)
+           {
+              last_parent=temp;
+           }
+       }
+       if(temp->right!=NULL)//if right subtree only present;
+       {
+           if(temp->right->left==NULL&&temp->right->right==NULL)
+           {
+              last_parent=temp;
+           }
+       }
+       
+       /*for storing the value of last node.*/
+       last_value=temp->data;
+       q.pop();
+       if(temp->left!=NULL)
+       {
+           q.push(temp->left);
+       }
+       if(temp->right!=NULL)
+       {
+           q.push(temp->right);
+       }
+   }
+   /*return the parent of last node and the data of the last node*/
+   return make_pair(last_parent,last_value);
+}
+void delete_node(Node* root,int value,int last_value)
+{
+    /*if only one node is present and we want to delete it*/
+    if(root->left==NULL&&root->right==NULL)
+    {
+        root=NULL;
+        return;
+    }
+    queue<Node*> q;
+    q.push(root);
+    while(!q.empty())
+    {
+        Node* temp=q.front();
+        q.pop();
+        /*if we find the node which we want to delete then change the data with last node data*/
+        if(temp->data==value)
+        {
+            temp->data=last_value;
+        }
+        if(temp->left!=NULL)
+        {
+           q.push(temp->left); 
+        }
+        if(temp->right!=NULL)
+        {
+            q.push(temp->right);
+        }
+    }
+}
 
 int main() 
 { 
-
+     
 	/*create root*/
 	struct Node* root = new Node(1); 
 	/* following is the tree after above statement 
-
 			1 
 			/ \ 
 			NULL NULL 
 	*/
-
+    
 	root->left = new Node(2); 
 	root->right = new Node(3); 
 	/* 2 and 3 become left and right children of 1 
@@ -51,6 +156,29 @@ int main()
 	/ \ 
 	NULL NULL 
 	*/
-
+	cout<<"Level order traversal before Deletion of node: ";
+    level_order(root);
+    
+    int value;
+    cout<<"Enter the value of node to be deleted"<<endl;
+    cin>>value;//input the data of node which we want to delete;
+    
+    /*Find the last node and its parent to remove last node from tree.*/
+    pair<Node*,int> last=last_node(root);
+    /*remove last node*/
+    if(last.first->left!=NULL&&last.first->left->data==last.second)
+    {
+        last.first->left=NULL;
+    }
+    if(last.first->right!=NULL&&last.first->right->data==last.second)
+    {
+        last.first->right=NULL;
+    }
+    /*delete the node*/
+    delete_node(root, value,last.second);
+    cout<<"Level order traversal after Deletion of node: ";
+    level_order(root);
+    
 	return 0; 
 } 
+