Get last node of the binary tree following given pattern starting from X

Given a binary tree, target node X and a string patt. The task is to find the last node of the binary tree following the pattern starting from X. Pattern may contain only five types of character ‘p’, ‘l’, ‘r’, ‘m’ and ‘n’. For any character encountered:

p: Get to the parent of the current node.
l: Get to the left child of the current node.
r: Get to the right child of the current node.
m: Get to the left sibling in the same level.
n: Get to the right sibling in the same level.

Note that if the node doesn’t exist corresponding to any character then skip that character and remain on the current node.

Examples:

Input:
         10 
        /   \ 
      12    13 
           /   \ 
         14     15 
        /  \    /  \ 
       21  22  23  24 

X = 14, patt = "npmrprrlm"
Output: 22
Starting from the target node 14
n: 14 -> 15
p: 15 -> 13
m: 13 -> 12
r: 12 -> 12 (there is no right child)
p: 12 -> 10
r: 10 -> 13
r: 13 -> 15
l: 15 -> 23
m: 23 -> 22

Input:
         5
        /  \ 
      16    8

X = 16, patt = "pppp"
Output: 5

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach:

Create an auxiliary tree from the original tree but include three extra pointers (parent pointer, left and right sibling pointers).
- Parent pointer will point to the parent of the current node.
- Left pointer will point to the left sibling.
- Right pointer will point to the right sibling.
Check the image below:
After creation of this tree, we can easily traverse the given pattern.
If any node doesn’t exist corresponding any character then simply skip that character.

Below is the implementation of the above approach:

C++

// C++ implementation of the approach 
#include <bits/stdc++.h> 
using namespace std; 
  
// A Tree node 
struct Node  
{ 
    int key; 
    struct Node *left, *right; 
}; 
  
// Utility function to create a new node 
Node* newNode(int key) 
{ 
    Node* temp = new Node; 
    temp->key = key; 
    temp->left = temp->right = NULL; 
    return (temp); 
} 
  
struct auxNode  
{ 
    int key; 
    auxNode *left, *right, *parent; 
  
    // Pointer will point the left node 
    // at the same level in the tree 
    auxNode* llNode; 
  
    // Pointer will point the right node 
    // at the same level in the tree 
    auxNode* rlNode; 
}; 
  
auxNode* newAuxNode(int key) 
{ 
    auxNode* temp = new auxNode; 
    temp->key = key; 
    temp->left = temp->right = temp->parent 
        = temp->llNode = temp->rlNode = NULL; 
    return temp; 
} 
  
// Function to create the auxiliary tree 
auxNode* createAuxTree(Node* root) 
{ 
    if (root == NULL) 
        return NULL; 
    auxNode* auxTree = newAuxNode(root->key); 
  
    auxTree->left = createAuxTree(root->left); 
    auxTree->right = createAuxTree(root->right); 
    return auxTree; 
} 
  
// Function for arranging the parent node for every node 
void makeParentNodePoint(auxNode* auxTree,  
                         auxNode* prev_ptr) 
{ 
    if (auxTree == NULL) 
        return; 
  
    // Set the parent 
    if (prev_ptr != NULL)  
    { 
        auxTree->parent = prev_ptr; 
    } 
  
    // Recur for left and right sub-trees 
    makeParentNodePoint(auxTree->left, auxTree); 
    makeParentNodePoint(auxTree->right, auxTree); 
} 
  
// Function for arranging the left and right 
// node for every node at the same level 
void makeSameLevelNodePoint(auxNode* auxTree) 
{ 
    queue<auxNode*> qu; 
    qu.push(auxTree); 
    while (!qu.empty()) 
    { 
        int qsize = qu.size(); 
        while (qsize--)  
        { 
            auxNode* top_ele; 
            top_ele = qu.front(); 
            qu.pop(); 
            if (qsize) 
            { 
                top_ele->rlNode = qu.front(); 
                qu.front()->llNode = top_ele; 
            } 
            if (top_ele->left != NULL) 
            { 
                qu.push(top_ele->left); 
            } 
            if (top_ele->right != NULL)  
            { 
                qu.push(top_ele->right); 
            } 
        } 
    } 
} 
  
// Function to return the target node address 
auxNode* getTargetNodeAddress(auxNode* auxTree, int tNode) 
{ 
    if (auxTree == NULL) 
        return NULL; 
  
    if (auxTree->key == tNode) 
    { 
        return auxTree; 
    } 
    auxNode* is_null = getTargetNodeAddress(auxTree->left, tNode); 
    if (is_null != NULL) 
        return is_null; 
    return getTargetNodeAddress(auxTree->right, tNode); 
} 
  
// Utility function to print the last node 
void printNode(auxNode* auxTree,  
               auxNode* target_node,  
               string pattern) 
{ 
  
    // Perform the movement 
    for (int i = 0; i < pattern.length(); i++)  
    { 
        switch (pattern[i]) 
        { 
  
        // Get to the parent 
        case 'p': 
        case 'P': 
            if (target_node->parent != NULL) 
            { 
                target_node = target_node->parent; 
            } 
            break; 
  
        // Get to the left child 
        case 'l': 
        case 'L': 
            if (target_node->left != NULL)  
            { 
                target_node = target_node->left; 
            } 
            break; 
  
        // Get to the right child 
        case 'r': 
        case 'R': 
            if (target_node->right != NULL) 
                target_node = target_node->right; 
            break; 
  
        // Get to the left sibling in the same level 
        case 'm': 
        case 'M': 
            if (target_node->llNode != NULL) 
                target_node = target_node->llNode; 
            break; 
  
        // Get to the right sibling in the same level 
        case 'n': 
        case 'N': 
            if (target_node->rlNode != NULL) 
                target_node = target_node->rlNode; 
            break; 
        default: 
            return; 
        } 
    } 
    cout << target_node->key; 
} 
  
// Function to print the last node  
// according to the pattern 
void printNodeUsingPattern(Node* root,  
                           string pattern, int tNode) 
{ 
    // Function will create auxiliary tree same as 
    // original tree with left child and right child 
    auxNode* auxTree = createAuxTree(root); 
  
    // Function will make every node  
    // point to its parent node 
    makeParentNodePoint(auxTree, NULL); 
  
    // Function will make every node point to its 
    // left and right node at the same level 
    makeSameLevelNodePoint(auxTree); 
  
    // Function will give the address of the target node 
    auxNode* target_node = getTargetNodeAddress(auxTree, tNode); 
  
    // If target node found 
    if (target_node != NULL) 
    { 
  
        // Function call to print the last node 
        // according to the given pattern 
        printNode(auxTree, target_node, pattern); 
    } 
    else
        cout << "-1";  
}  
    
// Driver code  
int main()  
{  
    Node* root = newNode(10);  
    root->left = newNode(12);  
    root->right = newNode(13);  
    root->right->left = newNode(14);  
    root->right->right = newNode(15);  
    root->right->left->left = newNode(21);  
    root->right->left->right = newNode(22);  
    root->right->right->left = newNode(23);  
    root->right->right->right = newNode(24);  
    int target_node = 14;  
    string str = "npmrprrlm";  
    printNodeUsingPattern(root, str, target_node);  
    
    return 0;  
}  

Python3

# Python3 implementation of the approach 
import queue 
  
# A Tree node 
class Node:  
    def __init__(self,key):  
        self.left = None
        self.right = None
        self.key = key 
          
class auxNode: 
    def __init__(self,key): 
        self.left = None
        self.right = None
        self.key = key 
        self.parent = None
  
        # Pointer will point the left node 
        # at the same level in the tree 
        self.llNode = None
  
        # Pointer will point the right node 
        # at the same level in the tree 
        self.rlNode = None
      
def newAuxNode(key): 
  
    temp = auxNode(key) 
    return temp 
  
def createAuxTree(root): 
  
    if (root == None) : 
        return None
      
    auxTree = auxNode(root.key) 
      
    auxTree.left = createAuxTree(root.left) 
    auxTree.right = createAuxTree(root.right) 
    return auxTree 
      
# Function for arranging the  
# parent node for every node 
def makeParentNodePoint(auxTree, prev_ptr): 
  
    if (auxTree == None): 
        return; 
  
    # Set the parent 
    if (prev_ptr != None) : 
        auxTree.parent = prev_ptr 
        #print("Parent : ",auxTree.parent.key) 
      
    # Recur for left and right sub-trees 
    makeParentNodePoint(auxTree.left, auxTree) 
    makeParentNodePoint(auxTree.right, auxTree) 
      
# Function for arranging the left and right 
# node for every node at the same level 
def makeSameLevelNodePoint(auxTree): 
  
    qu = queue.Queue(maxsize = 50) 
    qu.put(auxTree) 
    while (not qu.empty()) : 
        size = qu.qsize() 
        while (size) : 
            size -= 1
              
            top_ele = qu.get(); 
              
            if (size) : 
                front = qu.get() 
                top_ele.rlNode = front 
                front.llNode = top_ele 
                  
                # since we don't have peek function  
                # in python creating 2nd queue  
                # to store elements below peek element 
                qu2 = queue.Queue(maxsize = 50) 
                while not qu.empty(): 
                    a = qu.get() 
                    qu2.put(a) 
                      
                # putting back front element  
                # in queue 1 all elements which  
                # were behind it in original queue 
                qu.put(front) 
                while not qu2.empty(): 
                    qu.put(qu2.get()) 
              
            if (top_ele.left != None) : 
                qu.put(top_ele.left) 
              
            if (top_ele.right != None) : 
                qu.put(top_ele.right) 
                  
# Function to return the target node address 
def getTargetNodeAddress(auxTree, tNode): 
  
    if (auxTree == None): 
        return None
  
    if (auxTree.key == tNode) : 
        return auxTree 
      
    is_null = getTargetNodeAddress(auxTree.left, tNode) 
    if (is_null != None): 
        return is_null 
    return getTargetNodeAddress(auxTree.right, tNode) 
      
# Utility function to print the last node 
def printNode(auxTree, target_node, pattern): 
  
    # Perform the movement 
    for i in range(len(pattern)) : 
          
        # Get to the parent 
        if pattern[i] == 'p' or pattern[i] == 'P': 
      
            if (target_node.parent != None):  
                target_node = target_node.parent 
          
        # Get to the left child 
        elif pattern[i] == 'l' or pattern[i] == 'L': 
            if (target_node.left != None) : 
                target_node = target_node.left 
              
        # Get to the right child 
        elif pattern[i] == 'r' or pattern[i] == 'R': 
            if (target_node.right != None): 
                target_node = target_node.right 
              
        # Get to the left sibling in the same level 
        elif pattern[i] == 'm' or pattern[i] == 'M': 
            if (target_node.llNode != None): 
                target_node = target_node.llNode 
          
        # Get to the right sibling in the same level 
        elif pattern[i] == 'n' or pattern[i] == 'N': 
            if (target_node.rlNode != None): 
                target_node = target_node.rlNode 
        else: 
            return
  
    print(target_node.key, end = ' ') 
  
# Function to print the last node  
# according to the pattern 
def printNodeUsingPattern(root, pattern, tNode): 
      
    # Function will create auxiliary tree same as 
    # original tree with left child and right child 
    auxTree = createAuxTree(root) 
  
    # Function will make every node 
    # point to its parent node 
    makeParentNodePoint(auxTree, None) 
      
    # Function will make every node point to its 
    # left and right node at the same level 
    makeSameLevelNodePoint(auxTree) 
      
    # Function will give the address of the target node 
    target_node = getTargetNodeAddress(auxTree, tNode) 
  
    # If target node found 
    if (target_node != None) : 
  
        # Function call to print the last node 
        # according to the given pattern 
        printNode(auxTree, target_node, pattern); 
  
    else : 
        print("-1") 
  
# Driver Code 
root = Node(10)  
root.left = Node(12) 
root.right = Node(13) 
root.right.left = Node(14) 
root.right.right = Node(15) 
root.right.left.left = Node(21) 
root.right.left.right = Node(22) 
root.right.right.left = Node(23) 
root.right.right.right = Node(24) 
target_node = 14
string = "npmrprrlm"
  
printNodeUsingPattern(root, string, target_node) 
  
# This code is contributed by Sadik Ali  

Output:

My Personal Notes

Suggest a Topic

Recommended: Please try your approach on {IDE} first, before moving on to the solution.

C++

Python3

Recommended Posts: