Splay Tree | Set 2 (Insert)

• Difficulty Level : Medium
• Last Updated : 11 Aug, 2021

It is recommended to refer following post as prerequisite of this post.
Splay Tree | Set 1 (Search)
As discussed in the previous post, Splay tree is a self-balancing data structure where the last accessed key is always at root. The insert operation is similar to Binary Search Tree insert with additional steps to make sure that the newly inserted key becomes the new root.
Following are different cases to insert a key k in splay tree.
1) Root is NULL: We simply allocate a new node and return it as root.
2) Splay the given key k. If k is already present, then it becomes the new root. If not present, then last accessed leaf node becomes the new root.
3) If new root’s key is same as k, don’t do anything as k is already present.
4) Else allocate memory for new node and compare root’s key with k.
…….4.a) If k is smaller than root’s key, make root as right child of new node, copy left child of root as left child of new node and make left child of root as NULL.
…….4.b) If k is greater than root’s key, make root as left child of new node, copy right child of root as right child of new node and make right child of root as NULL.
5) Return new node as new root of tree.
Example:

100                                               25
/  \                   \                             /  \
50   200                  50                          20   50
/          insert(25)     /  \        insert(25)           /  \
40          ======>      30   100      ========>           30  100
/          1. Splay(25)    \     \      2. insert 25         \    \
30                          40    200                         40   200
/


C++

 #include using namespace std; // An AVL tree nodeclass node{    public:    int key;    node *left, *right;}; /* Helper function that allocatesa new node with the given key and    NULL left and right pointers. */node* newNode(int key){    node* Node = new node();    Node->key = key;    Node->left = Node->right = NULL;    return (Node);} // A utility function to right// rotate subtree rooted with y// See the diagram given above.node *rightRotate(node *x){    node *y = x->left;    x->left = y->right;    y->right = x;    return y;} // A utility function to left// rotate subtree rooted with x// See the diagram given above.node *leftRotate(node *x){    node *y = x->right;    x->right = y->left;    y->left = x;    return y;} // This function brings the key at// root if key is present in tree.// If key is not present, then it// brings the last accessed item at// root. This function modifies the// tree and returns the new rootnode *splay(node *root, int key){    // Base cases: root is NULL or    // key is present at root    if (root == NULL || root->key == key)        return root;     // Key lies in left subtree    if (root->key > key)    {        // Key is not in tree, we are done        if (root->left == NULL) return root;         // Zig-Zig (Left Left)        if (root->left->key > key)        {            // First recursively bring the            // key as root of left-left            root->left->left = splay(root->left->left, key);             // Do first rotation for root,            // second rotation is done after else            root = rightRotate(root);        }        else if (root->left->key < key) // Zig-Zag (Left Right)        {            // First recursively bring            // the key as root of left-right            root->left->right = splay(root->left->right, key);             // Do first rotation for root->left            if (root->left->right != NULL)                root->left = leftRotate(root->left);        }         // Do second rotation for root        return (root->left == NULL)? root: rightRotate(root);    }    else // Key lies in right subtree    {        // Key is not in tree, we are done        if (root->right == NULL) return root;         // Zig-Zag (Right Left)        if (root->right->key > key)        {            // Bring the key as root of right-left            root->right->left = splay(root->right->left, key);             // Do first rotation for root->right            if (root->right->left != NULL)                root->right = rightRotate(root->right);        }        else if (root->right->key < key)// Zag-Zag (Right Right)        {            // Bring the key as root of            // right-right and do first rotation            root->right->right = splay(root->right->right, key);            root = leftRotate(root);        }         // Do second rotation for root        return (root->right == NULL)? root: leftRotate(root);    }} // Function to insert a new key k// in splay tree with given rootnode *insert(node *root, int k){    // Simple Case: If tree is empty    if (root == NULL) return newNode(k);     // Bring the closest leaf node to root    root = splay(root, k);     // If key is already present, then return    if (root->key == k) return root;     // Otherwise allocate memory for new node    node *newnode = newNode(k);     // If root's key is greater, make    // root as right child of newnode    // and copy the left child of root to newnode    if (root->key > k)    {        newnode->right = root;        newnode->left = root->left;        root->left = NULL;    }     // If root's key is smaller, make    // root as left child of newnode    // and copy the right child of root to newnode    else    {        newnode->left = root;        newnode->right = root->right;        root->right = NULL;    }     return newnode; // newnode becomes new root} // A utility function to print// preorder traversal of the tree.// The function also prints height of every nodevoid preOrder(node *root){    if (root != NULL)    {        cout<key<<" ";        preOrder(root->left);        preOrder(root->right);    }} /* Driver code*/int main(){    node *root = newNode(100);    root->left = newNode(50);    root->right = newNode(200);    root->left->left = newNode(40);    root->left->left->left = newNode(30);    root->left->left->left->left = newNode(20);    root = insert(root, 25);    cout<<"Preorder traversal of the modified Splay tree is \n";    preOrder(root);    return 0;} // This code is contributed by rathbhupendra

C

 // This code is adopted from http://algs4.cs.princeton.edu/33balanced/SplayBST.java.html#include#include // An AVL tree nodestruct node{    int key;    struct node *left, *right;}; /* Helper function that allocates a new node with the given key and    NULL left and right pointers. */struct node* newNode(int key){    struct node* node = (struct node*)malloc(sizeof(struct node));    node->key   = key;    node->left  = node->right  = NULL;    return (node);} // A utility function to right rotate subtree rooted with y// See the diagram given above.struct node *rightRotate(struct node *x){    struct node *y = x->left;    x->left = y->right;    y->right = x;    return y;} // A utility function to left rotate subtree rooted with x// See the diagram given above.struct node *leftRotate(struct node *x){    struct node *y = x->right;    x->right = y->left;    y->left = x;    return y;} // This function brings the key at root if key is present in tree.// If key is not present, then it brings the last accessed item at// root.  This function modifies the tree and returns the new rootstruct node *splay(struct node *root, int key){    // Base cases: root is NULL or key is present at root    if (root == NULL || root->key == key)        return root;     // Key lies in left subtree    if (root->key > key)    {        // Key is not in tree, we are done        if (root->left == NULL) return root;         // Zig-Zig (Left Left)        if (root->left->key > key)        {            // First recursively bring the key as root of left-left            root->left->left = splay(root->left->left, key);             // Do first rotation for root, second rotation is done after else            root = rightRotate(root);        }        else if (root->left->key < key) // Zig-Zag (Left Right)        {            // First recursively bring the key as root of left-right            root->left->right = splay(root->left->right, key);             // Do first rotation for root->left            if (root->left->right != NULL)                root->left = leftRotate(root->left);        }         // Do second rotation for root        return (root->left == NULL)? root: rightRotate(root);    }    else // Key lies in right subtree    {        // Key is not in tree, we are done        if (root->right == NULL) return root;         // Zig-Zag (Right Left)        if (root->right->key > key)        {            // Bring the key as root of right-left            root->right->left = splay(root->right->left, key);             // Do first rotation for root->right            if (root->right->left != NULL)                root->right = rightRotate(root->right);        }        else if (root->right->key < key)// Zag-Zag (Right Right)        {            // Bring the key as root of right-right and do first rotation            root->right->right = splay(root->right->right, key);            root = leftRotate(root);        }         // Do second rotation for root        return (root->right == NULL)? root: leftRotate(root);    }} // Function to insert a new key k in splay tree with given rootstruct node *insert(struct node *root, int k){    // Simple Case: If tree is empty    if (root == NULL) return newNode(k);     // Bring the closest leaf node to root    root = splay(root, k);     // If key is already present, then return    if (root->key == k) return root;     // Otherwise allocate memory for new node    struct node *newnode  = newNode(k);     // If root's key is greater, make root as right child    // of newnode and copy the left child of root to newnode    if (root->key > k)    {        newnode->right = root;        newnode->left = root->left;        root->left = NULL;    }     // If root's key is smaller, make root as left child    // of newnode and copy the right child of root to newnode    else    {        newnode->left = root;        newnode->right = root->right;        root->right = NULL;    }     return newnode; // newnode becomes new root} // A utility function to print preorder traversal of the tree.// The function also prints height of every nodevoid preOrder(struct node *root){    if (root != NULL)    {        printf("%d ", root->key);        preOrder(root->left);        preOrder(root->right);    }} /* Driver program to test above function*/int main(){    struct node *root = newNode(100);    root->left = newNode(50);    root->right = newNode(200);    root->left->left = newNode(40);    root->left->left->left = newNode(30);    root->left->left->left->left = newNode(20);    root = insert(root, 25);    printf("Preorder traversal of the modified Splay tree is \n");    preOrder(root);    return 0;}

Java

 import java.util.*; class GFG{ // An AVL tree nodestatic class node{     int key;    node left, right;}; /* Helper function that allocatesa new node with the given key and    null left and right pointers. */static node newNode(int key){    node Node = new node();    Node.key = key;    Node.left = Node.right = null;    return (Node);} // A utility function to right// rotate subtree rooted with y// See the diagram given above.static node rightRotate(node x){    node y = x.left;    x.left = y.right;    y.right = x;    return y;} // A utility function to left// rotate subtree rooted with x// See the diagram given above.static node leftRotate(node x){    node y = x.right;    x.right = y.left;    y.left = x;    return y;} // This function brings the key at// root if key is present in tree.// If key is not present, then it// brings the last accessed item at// root. This function modifies the// tree and returns the new rootstatic node splay(node root, int key){    // Base cases: root is null or    // key is present at root    if (root == null || root.key == key)        return root;     // Key lies in left subtree    if (root.key > key)    {        // Key is not in tree, we are done        if (root.left == null) return root;         // Zig-Zig (Left Left)        if (root.left.key > key)        {            // First recursively bring the            // key as root of left-left            root.left.left = splay(root.left.left, key);             // Do first rotation for root,            // second rotation is done after else            root = rightRotate(root);        }        else if (root.left.key < key) // Zig-Zag (Left Right)        {            // First recursively bring            // the key as root of left-right            root.left.right = splay(root.left.right, key);             // Do first rotation for root.left            if (root.left.right != null)                root.left = leftRotate(root.left);        }         // Do second rotation for root        return (root.left == null)? root: rightRotate(root);    }    else // Key lies in right subtree    {        // Key is not in tree, we are done        if (root.right == null) return root;         // Zig-Zag (Right Left)        if (root.right.key > key)        {            // Bring the key as root of right-left            root.right.left = splay(root.right.left, key);             // Do first rotation for root.right            if (root.right.left != null)                root.right = rightRotate(root.right);        }        else if (root.right.key < key)// Zag-Zag (Right Right)        {            // Bring the key as root of            // right-right and do first rotation            root.right.right = splay(root.right.right, key);            root = leftRotate(root);        }         // Do second rotation for root        return (root.right == null)? root: leftRotate(root);    }} // Function to insert a new key k// in splay tree with given rootstatic node insert(node root, int k){    // Simple Case: If tree is empty    if (root == null) return newNode(k);     // Bring the closest leaf node to root    root = splay(root, k);     // If key is already present, then return    if (root.key == k) return root;     // Otherwise allocate memory for new node    node newnode = newNode(k);     // If root's key is greater, make    // root as right child of newnode    // and copy the left child of root to newnode    if (root.key > k)    {        newnode.right = root;        newnode.left = root.left;        root.left = null;    }     // If root's key is smaller, make    // root as left child of newnode    // and copy the right child of root to newnode    else    {        newnode.left = root;        newnode.right = root.right;        root.right = null;    }     return newnode; // newnode becomes new root} // A utility function to print// preorder traversal of the tree.// The function also prints height of every nodestatic void preOrder(node root){    if (root != null)    {        System.out.print(root.key+" ");        preOrder(root.left);        preOrder(root.right);    }} /* Driver code*/public static void main(String[] args){    node root = newNode(100);    root.left = newNode(50);    root.right =  newNode(200);    root.left.left =  newNode(40);    root.left.left.left =  newNode(30);    root.left.left.left.left =  newNode(20);    root = insert(root, 25);    System.out.print("Preorder traversal of the modified Splay tree is \n");    preOrder(root);}}  // This code is contributed by Rajput-Ji

C#

 using System; public class node{  public int key;  public node left, right;   } public class GFG{   /* Helper function that allocatesa new node with the given key and    null left and right pointers. */  static node newNode(int key)  {    node Node = new node();    Node.key = key;    Node.left = Node.right = null;    return (Node);  }   // A utility function to right  // rotate subtree rooted with y  // See the diagram given above.  static node rightRotate(node x)  {    node y = x.left;    x.left = y.right;    y.right = x;    return y;  }   // A utility function to left  // rotate subtree rooted with x  // See the diagram given above.  static node leftRotate(node x)  {    node y = x.right;    x.right = y.left;    y.left = x;    return y;  }   // This function brings the key at  // root if key is present in tree.  // If key is not present, then it  // brings the last accessed item at  // root. This function modifies the  // tree and returns the new root  static node splay(node root, int key)  {    // Base cases: root is null or    // key is present at root    if (root == null || root.key == key)      return root;     // Key lies in left subtree    if (root.key > key)    {      // Key is not in tree, we are done      if (root.left == null) return root;       // Zig-Zig (Left Left)      if (root.left.key > key)      {        // First recursively bring the        // key as root of left-left        root.left.left = splay(root.left.left, key);         // Do first rotation for root,        // second rotation is done after else        root = rightRotate(root);      }      else if (root.left.key < key) // Zig-Zag (Left Right)      {        // First recursively bring        // the key as root of left-right        root.left.right = splay(root.left.right, key);         // Do first rotation for root.left        if (root.left.right != null)          root.left = leftRotate(root.left);      }       // Do second rotation for root      return (root.left == null)? root: rightRotate(root);    }    else // Key lies in right subtree    {      // Key is not in tree, we are done      if (root.right == null) return root;       // Zig-Zag (Right Left)      if (root.right.key > key)      {        // Bring the key as root of right-left        root.right.left = splay(root.right.left, key);         // Do first rotation for root.right        if (root.right.left != null)          root.right = rightRotate(root.right);      }      else if (root.right.key < key)// Zag-Zag (Right Right)      {        // Bring the key as root of        // right-right and do first rotation        root.right.right = splay(root.right.right, key);        root = leftRotate(root);      }       // Do second rotation for root      return (root.right == null)? root: leftRotate(root);    }  }   // Function to insert a new key k  // in splay tree with given root  static node insert(node root, int k)  {    // Simple Case: If tree is empty    if (root == null) return newNode(k);     // Bring the closest leaf node to root    root = splay(root, k);     // If key is already present, then return    if (root.key == k) return root;     // Otherwise allocate memory for new node    node newnode = newNode(k);     // If root's key is greater, make    // root as right child of newnode    // and copy the left child of root to newnode    if (root.key > k)    {      newnode.right = root;      newnode.left = root.left;      root.left = null;    }     // If root's key is smaller, make    // root as left child of newnode    // and copy the right child of root to newnode    else    {      newnode.left = root;      newnode.right = root.right;      root.right = null;    }     return newnode; // newnode becomes new root  }   // A utility function to print  // preorder traversal of the tree.  // The function also prints height of every node  static void preOrder(node root)  {    if (root != null)    {      Console.Write(root.key+" ");      preOrder(root.left);      preOrder(root.right);    }  }   /* Driver code*/  static public void Main ()  {     node root = newNode(100);    root.left = newNode(50);    root.right =  newNode(200);    root.left.left =  newNode(40);    root.left.left.left =  newNode(30);    root.left.left.left.left =  newNode(20);    root = insert(root, 25);    Console.Write("Preorder traversal of the modified Splay tree is \n");    preOrder(root);  }} // This code is contributed by patel2127.

Javascript



Output:

Preorder traversal of the modified Splay tree is
25 20 50 30 40 100 200