Data Structure
Networking
RDBMS
Operating System
Java
MS Excel
iOS
HTML
CSS
Android
Python
C Programming
C++
C#
MongoDB
MySQL
Javascript
PHP
Economics & Finance
Suppose we have a list called relations, where each element relations[i] contains two numbers [ai, bi] indicating that person ai is following bi on a social media platform. We need to find mutual followers − people who follow someone and are followed back by them. The result should be returned in sorted order. So, if the input is like relations = [[0, 2], [2, 3], [2, 0], [1, 0]], then the output will be [0, 2] because person 0 follows person 2, and person 2 follows person 0 back. Algorithm To solve this, we will follow these ... Read More
Suppose we have a lowercase string s. We need to find the minimum number of contiguous substrings that s can be divided into, where each substring is either non-increasing (monotonically decreasing) or non-decreasing (monotonically increasing). For example, "pqqqr" is a non-decreasing string, and "qqqp" is a non-increasing string. Problem Example If the input is s = "pqrsrqp", then the output will be 2, because we can break s into "pqrs" (non-decreasing) and "rqp" (non-increasing). Algorithm Steps To solve this problem, we follow these steps ? If string is empty, ... Read More
Suppose we have a list of numbers called nums. We have to find the minimum positive value that we can insert at the beginning of nums so that the prefix sums of the resulting list are all positive (greater than 0). So, if the input is like nums = [3, -6, 4, 3], then the output will be 4, because if we insert 4 to the list then we have [4, 3, -6, 4, 3]. Now the prefix sums are [4, 7, 1, 5, 8], all are positive. Algorithm To solve this, we will follow these steps ... Read More
Finding the minimum distance between two words in a text is a common string processing problem. The distance is measured as the number of words between any occurrence of the two target words. Given a text string and two words w1 and w2, we need to find the smallest number of words between any occurrences of these words. If either word is not present, we return -1. Algorithm The approach involves tracking the most recent positions of both words as we iterate through the text ? Initialize index1 and index2 as None Set distance to ... Read More
Given a list of numbers and a value k, we need to find the minimum amplitude (difference between maximum and minimum) after removing k elements from the list. So, if the input is like nums = [4, 10, 3, 2, 8, 9] and k = 3, then the output will be 2. If we remove 10, 8, and 9, the remaining elements are [4, 3, 2], where maximum is 4 and minimum is 2, giving us an amplitude of 2. Algorithm To solve this problem, we will follow these steps ? ... Read More
Given an array of numbers, we need to find the maximum product of two distinct elements. The key insight is that the maximum product can come from either the two largest numbers or the two smallest numbers (if they are both negative). For example, if the input is nums = [8, -3, 1, -5], the output will be 15 because (-3) * (-5) = 15, which is the maximum product possible. Approach To solve this problem, we follow these steps ? Sort the array to get elements in ascending order ... Read More
Suppose we have a list of numbers called nums, we have to find the largest product of three unique elements. So, if the input is like nums = [6, 1, 2, 4, -3, -4], then the output will be 72, as we can multiply (-3) * (-4) * 6 = 72. Algorithm To solve this, we will follow these steps − Sort the list nums n := size of nums maxScore := -infinity maxScore := maximum of maxScore and ... Read More
Given two lists nums and multipliers, we need to find the maximum sum by pairing and multiplying elements from both lists. We can remove any number from either list and multiply them together, repeating until one list is empty. The key insight is to pair negative multipliers with the smallest numbers and positive multipliers with the largest numbers to maximize the sum. Algorithm To solve this problem, we follow these steps: Sort both lists in ascending order Ensure nums is the longer list (swap if needed) For each multiplier: If multiplier ≤ 0: pair ... Read More
Suppose we have a list with only 0s and 1s called seats, where seats[i] represents a seat. When it is 1, the seat is occupied; otherwise, it's free. Given that there is at least one free seat and at least one occupied seat, we need to find the maximum distance from a free seat to the nearest occupied seat. For example, if the input is seats = [1, 0, 1, 0, 0, 0, 1], the output will be 2, because we can occupy seat seats[4], and the distance to the nearest occupied seat is 2. Algorithm Approach ... Read More
Suppose we have n different nodes, all distinct. We need to find how many ways we can arrange them to form a Binary Search Tree (BST). In a BST, the left subtree always holds smaller values and the right subtree holds greater values. To solve this problem, we use Catalan numbers. The Catalan number C(n) represents the number of structurally different binary search trees with n different keys. Catalan Number Formula The formula for the nth Catalan number is: C(n) = (2n)! / ((n+1)! × n!) Alternatively, it can be calculated as: C(n) = ... Read More