C++ code to reverse paths in a binary search tree using queues

For example, given a binary search tree, we need to reverse its path from a specific key.

Ways to find solution

In this method we will create a queue and push all the nodes , until the root node is obtained.

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Example

 
#include <bits/stdc++.h>
using namespace std;
struct node {
   int key;
   struct node *left, *right;
};
struct node* newNode(int item){
   struct node* temp = new node;
   temp->key = item;
   temp->left = temp->right = NULL;
   return temp;
}
void inorder(struct node* root){
   if (root != NULL) {
       inorder(root->left);
       cout << root->key << " ";
       inorder(root->right);
   }
}
void Reversing(struct node** node,
           int& key, queue<int>& q1){
   /* If the tree is empty then
   return*/
   if (node == NULL)
       return;
   if ((*node)->key == key){ // if we find the key
       q1.push((*node)->key); // we push it into our queue
       (*node)->key = q1.front(); // we change the first queue element with current
       q1.pop(); // we pop the first element
   }
   else if (key < (*node)->key){ // if key is less than current node&#39;s value
       q1.push((*node)->key); // we push the element in our queue
       Reversing(&(*node)->left, key, q1); //we go to the left subtree using a recursive call
       (*node)->key = q1.front(); //we reverse the elements
       q1.pop(); // we pop the first element
   }
   else if (key > (*node)->key){ // if key greater than node key then
       q1.push((*node)->key);// we push node key into queue
       Reversing(&(*node)->right, key, q1);// we go to right subtree using a recursive call
       (*node)->key = q1.front();// replace queue front to node key
       q1.pop(); // we pop the first element
   }
   return;
}
struct node* insert_node(struct node* node, // function to insert node nodes in our BST
                           int key){
   if (node == NULL)
       return newNode(key); // if tree is empty we return a new node
   if (key < node->key) // else we push that in our tree
       node->left = insert_node(node->left, key);
   else if (key > node->key)
       node->right = insert_node(node->right, key);
   return node; // returning the node
}
int main(){
   struct node* root = NULL;
   queue<int> q1;
   int k = 80;
/****************Creating the BST*************************/
   root = insert_node(root, 50);
   insert_node(root, 30);
   insert_node(root, 20);
   insert_node(root, 40);
   insert_node(root, 70);
   insert_node(root, 60);
   insert_node(root, 80);
   cout << "Before Reversing :" << "\n";
   inorder(root);
   cout << "\n";
   Reversing(&root, k, q1);
   cout << "After Reversing :" << "\n";
   // print inorder of reverse path tree
   inorder(root);
   return 0;
}

Output

Before Reversing :
20 30 40 50 60 70 80
After Reversing :
20 30 40 80 60 70 50

Explanation of the above code

In this method we just search for the given key. When we traverse the tree, we put all the nodes into a queue, now when we find the node with the key value, we swap the values ​​of all the path nodes that came before, in this process, our path

Conclusion

We solved the problem of reversing paths in BST using queues and recursion. We also learned the C program for this problem and the complete method (general) to solve it. We can write the same program in other languages ​​such as C, java, python and other languages. We hope you found this tutorial helpful.

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