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In this video, we will explore how to generate all possible letter combinations from a given set of digits on a mobile keypad. The approach leverages recursion and backtracking to build combinations by appending letters corresponding to each digit in the input array. We begin by handling the base case when the prefix length matches the size of the input array, and then proceed to recursively add letters from the mapping for each digit. The digits that are invalid (0 and 1) are skipped to ensure only valid combinations are generated.Furthermore, we will demonstrate how this method works using a C++ implementation that uses a pad map to convert digits into their corresponding letters. The solution operates efficiently by appending valid letters and backtracking when necessary. The final output will be a list of all possible words that the digits could represent, such as "ad, ae, af, bd, be, bf, cd, ce, cf" for the input [2, 3]. Watch the video to see the step-by-step implementation and understand the time and space complexities involved. For more details, please go through - <a href="https://www.geeksforgeeks.org/find-possible-words-phone-digits/">Print all possible words from phone digits</a>

Print all Possible Words from Phone Digits

In this video, we will explore different approaches to solve the N-Queens problem and find all distinct solutions. We begin by discussing a naive approach that generates all possible permutations of queen placements using recursion and checks for conflicts. This method takes O(n!*n) time and O(n) space. Additionally, we delve into an expected approach using backtracking with pruning to optimize the solution by incrementally building the configuration and pruning conflicts early. This approach reduces unnecessary calculations and operates in O(n!) time and O(n) space.Furthermore, the video explains an alternate approach using bit-masking to efficiently track occupied rows and diagonals during the backtracking process. Bit-masking allows for fast bitwise operations to manage the board's state, making it particularly efficient for larger values of n. This method also runs in O(n!) time and O(n) space. Watch the video to understand these methods in detail and how they help in solving the N-Queens problem optimally with different techniques. For more details, please go through - <a href="https://www.geeksforgeeks.org/printing-solutions-n-queen-problem/">Printing all solutions in N-Queen Problem</a>

N-Queens Problem

In this video, we will explore different approaches to calculate pow(b, e) where b is the base and e is the exponent. We begin by discussing the naive iterative approach, where we multiply the base b by itself exactly e times, followed by a recursive approach to calculate power. Additionally, we delve into the expected approach, which utilizes divide and conquer for efficient calculation by halving the exponent at each step.Furthermore, the video explains how to use built-in functions in languages like C++ and Python to compute the power in optimal time complexity. By using the pow() function or the ** operator, we can quickly compute the power with minimal computational cost. Watch the video to understand these methods and their time complexities, including O(e) for naive methods and O(log e) for divide and conquer. For more details, please go through - <a href="https://www.geeksforgeeks.org/write-a-c-program-to-calculate-powxn/">Write program to calculate pow(b, e)</a>

Program to Calculate pow(b, e)

A permutation also called an “arrangement number” or “order,” is a rearrangement of the elements of an ordered list S into a one-to-one correspondence with S itself. A string of length n has n! permutation.O(n*n!) Note that there are n! permutations and it requires O(n) time to print a permutation.Write a program to print all permutations of a given string: <a href="https://www.geeksforgeeks.org/write-a-c-program-to-print-all-permutations-of-a-given-string/">https://www.geeksforgeeks.org/write-a-c-program-to-print-all-permutations-of-a-given-string/</a>

Write a program to print all permutations of a given string

The simple approach is to create a list and add all values from 1 to n to it. Create a recursive function that takes a list, start (position at which counting will start), and k ( number of people to be skipped) as an argument. If the size of the list is one i.e. only one person left then return this position.&nbsp;Otherwise, start counting the k person in a clockwise direction from starting position and remove the person at the kth position. Now the person at the kth position is removed and now counting will start from this position. This process continues till only one person is left.Josephus Problem : <a href="https://www.geeksforgeeks.org/josephus-problem-set-1-a-on-solution/">https://www.geeksforgeeks.org/josephus-problem-set-1-a-on-solution/</a>

Josephus Problem

This video is part of the Recursion and Backtracking section under GFG SDE Sheet. Imagine you have a special keyboard with the following keys:&nbsp;Key 1: &nbsp;Prints 'A' on screen Key 2: (Ctrl-A): Select screen Key 3: (Ctrl-C): Copy selection to buffer Key 4: (Ctrl-V): Print buffer on screen appending it after what has already been printed.Find maximum numbers of A's that can be produced by pressing keys on the special keyboard N times.&nbsp; Example 1:Input: N = 3
 Output: 3
 Explanation: Press key 1 three times. Try it out before watching the implementation of the problem in the video. We recommend watching the video, even if you can solve the problem. You may discover something new. All the best!!!Do check out:- Problem: <a href="https://www.geeksforgeeks.org/problems/special-keyboard3018/1">https://www.geeksforgeeks.org/problems/special-keyboard3018/1</a> SDE Sheet Link: <a href="https://www.geeksforgeeks.org/sde-sheet-a-complete-guide-for-sde-preparation/">https://www.geeksforgeeks.org/sde-sheet-a-complete-guide-for-sde-preparation/</a> Article Link: <a href="https://www.geeksforgeeks.org/how-to-print-maximum-number-of-a-using-given-four-keys/">https://www.geeksforgeeks.org/how-to-print-maximum-number-of-a-using-given-four-keys/</a>

SDE Sheet - Special Keyboard

Welcome to the daily solving of our PROBLEM OF THE DAY with Saurabh Bansal We will discuss the entire problem step-by-step and work towards developing an optimized solution. This will not only help you brush up on your concepts of Dynamic Programming but also build up problem-solving skills. Given two strings&nbsp;pattern and&nbsp;str which may be of different size, You have to return 1 if the wildcard pattern i.e. pattern, matches&nbsp;with str else return 0. All characters of the string str and pattern always belong to the Alphanumeric characters.The wildcard pattern can include the characters ? and * ‘?’ – matches any single character. ‘*’ – Matches any sequence of characters (including the empty sequence).Note:&nbsp;The matching should cover the entire str (not partial str).Examples:Input: pattern = "ba*a?", str = "baaabab"
Output: 1
Explanation: replace '*' with "aab" and 
'?' with 'b'.Give the problem a try before going through the video. All the best!!! Problem Link: <a href="https://practice.geeksforgeeks.org/problems/wildcard-pattern-matching/1">https://practice.geeksforgeeks.org/problems/wildcard-pattern-matching/1</a>

PROBLEM OF THE DAY : 26/08/2024 | Wildcard Pattern Matching

Given a queue, write a recursive function to reverse it.&nbsp; Standard operations allowed :&nbsp; enqueue(x) : Add an item x to rear of queue.&nbsp; dequeue() : Remove an item from front of queue.&nbsp; empty() : Checks if a queue is empty or not. Examples :&nbsp; &nbsp;Input : Q = [5, 24, 9, 6, 8, 4, 1, 8, 3, 6] Output : Q = [6, 3, 8, 1, 4, 8, 6, 9, 24, 5]&nbsp;Reversing a queue using recursion : <a href="https://www.geeksforgeeks.org/reversing-queue-using-recursion/">https://www.geeksforgeeks.org/reversing-queue-using-recursion/</a>

Reversing a queue using recursion

Tower of Hanoi is a mathematical puzzle where we have three rods and n disks. The objective of the puzzle is to move the entire stack to another rod, obeying the following simple rules:Only one disk can be moved at a time. Each move consists of taking the upper disk from one of the stacks and placing it on top of another stack i.e. a disk can only be moved if it is the uppermost disk on a stack. No disk may be placed on top of a smaller disk. Approach :Let rod 1 = 'A', rod 2 = 'B', rod 3 = 'C'. An example with 2 disks : Step 1 : Shift first disk from 'A' to 'B'.Tower of Hanoi &nbsp;: <a href="https://www.geeksforgeeks.org/c-program-for-tower-of-hanoi/">https://www.geeksforgeeks.org/c-program-for-tower-of-hanoi/</a>

Tower of Hanoi

Given a Binary Tree find the length of the longest path which comprises of nodes with consecutive values in increasing order. Every node is considered as a path of length 1. We can solve above problem recursively. At each node we need information of its parent node, if current node has value one more than its parent node then it makes a consecutive path, at each node we will compare node’s value with its parent value and update the longest consecutive path accordingly.&nbsp; For getting the value of parent node, we will pass the (node_value + 1) as an argument to the recursive method and compare the node value with this argument value, if satisfies, update the current length of consecutive path otherwise reinitialize current path length by 1. Longest consecutive sequence in Binary tree: <a href="https://www.geeksforgeeks.org/longest-consecutive-sequence-binary-tree/">https://www.geeksforgeeks.org/longest-consecutive-sequence-binary-tree/</a>

Longest consecutive sequence in Binary tree

This video is part of the Recursion and Backtracking section under GFG SDE Sheet. The <a target="_blank" rel="noopener noreferrer nofollow" href="https://en.wikipedia.org/wiki/Tower_of_Hanoi">tower of Hanoi</a> is a famous puzzle where we have three rods and n disks. The objective of the puzzle is to move the entire stack to another rod. You are given the number of discs n. Initially, these discs are in the rod 1. You need to print all the steps of discs movement so that all the discs reach the 3rd rod. Also, you need to find the total moves.You only need to complete the function&nbsp;toh() that takes following parameters: n (number of discs),&nbsp;from&nbsp;(The rod number from which we move the disc),&nbsp;to&nbsp;(The rod number to which we move the disc),&nbsp;aux&nbsp;(The rod that is used as an auxiliary rod) and prints the required moves inside function body (See the example for the format of the output) as well as return the count of total moves made.Note: The discs are arranged such that the top disc is numbered 1 and the bottom-most disc is numbered n. Also, all the discs have different sizes and a bigger disc cannot be put on the top of a smaller disc. Refer the provided link to get a better clarity about the puzzle.Examples:Input:
n = 2
 Output:
 move disk 1 from rod 1 to rod 2
 move disk 2 from rod 1 to rod 3
 move disk 1 from rod 2 to rod 3
3
 Explanation: For N=2 , steps will be as follows in the example and total 3 steps will be taken. Try it out before watching the implementation of the problem in the video. We recommend watching the video, even if you can solve the problem. You may discover something new. All the best!!!Do check out:- Problem: <a href="https://www.geeksforgeeks.org/problems/tower-of-hanoi-1587115621/1">https://www.geeksforgeeks.org/problems/tower-of-hanoi-1587115621/1</a> SDE Sheet Link: <a href="https://www.geeksforgeeks.org/sde-sheet-a-complete-guide-for-sde-preparation/">https://www.geeksforgeeks.org/sde-sheet-a-complete-guide-for-sde-preparation/</a> Article Link: <a href="https://www.geeksforgeeks.org/c-program-for-tower-of-hanoi/">https://www.geeksforgeeks.org/c-program-for-tower-of-hanoi/</a>

SDE Sheet - Tower Of Hanoi

Welcome to the daily solving of our PROBLEM OF THE DAY with Yash Dwivedi. We will discuss the entire problem step-by-step and work towards developing an optimized solution. This will not only help you brush up on your concepts of Tree but also build up problem-solving skills. Given a binary tree, your task is to find all duplicate subtrees from the given binary tree.Duplicate Subtree : Two trees are duplicates if they have the same structure with the same node values.Note:&nbsp; Return the root of each tree in the form of a list array &amp; the driver code will print the tree in pre-order tree traversal in lexicographically increasing order.Examples: Input :&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;1 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; / &nbsp;\ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 2 &nbsp; &nbsp; 3 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; / &nbsp; &nbsp; &nbsp;/ &nbsp;\ &nbsp; &nbsp; &nbsp; &nbsp; 4 &nbsp; &nbsp; 2 &nbsp; &nbsp; &nbsp;4 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;/ &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; 4 Output: 2 &nbsp;4 &nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;4 Explanation: The above tree have two duplicate subtrees.i.e&nbsp; &nbsp; 2 &nbsp;/ 4 &nbsp;and 4. Therefore, you need to return the above tree root in the form of a list.Give the problem a try before going through the video. All the best!!! Problem Link: <a href="https://practice.geeksforgeeks.org/problems/duplicate-subtrees/1">https://practice.geeksforgeeks.org/problems/duplicate-subtrees/1</a>

PROBLEM OF THE DAY : 04/07/2024 | Duplicate Subtrees