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Articles by Arnab Chakraborty
Page 115 of 377
Program to count number of ways we can throw n dices in Python
Sometimes we need to find the number of ways to throw n dice with a specific number of faces to achieve a target total. This is a classic dynamic programming problem that can be solved efficiently using bottom-up approach. Problem Statement Given n dice, each with a specific number of faces, find how many ways we can throw them to get a target total. Since the answer can be very large, return the result modulo 10^9 + 7. For example, if n = 2, faces = 6, and total = 8, there are 5 ways: (2, 6), ...
Read MoreProgram to find sum each of the diagonal path elements in a binary tree in Python
In this problem, we need to find the sum of elements along each diagonal path in a binary tree. A diagonal path moves from top-left to bottom-right, where moving to the right child continues the same diagonal, while moving to the left child starts a new diagonal level. Looking at the example tree structure: 12 8 15 3 10 ...
Read MoreProgram to sort each diagonal elements in ascending order of a matrix in C++
Matrix diagonal sorting is a problem where we need to sort each diagonal of a matrix from top-left to bottom-right in ascending order. Each diagonal runs parallel to the main diagonal and gets sorted independently. Understanding the Problem Given a matrix, we identify all diagonals that run from top-left to bottom-right. For example, in a 3x4 matrix, we have multiple diagonals starting from different positions. ...
Read MoreProgram to find number of moves to win deleting repeated integer game in Python
Suppose two friends Amal and Bimal are playing a game with a sorted list of numbers called nums. In this game in a single turn, Amal chooses any three numbers. Bimal removes one of them, and then Amal removes one of them. The list starts out with an odd number of elements. Here Amal wishes to minimize the number of turns required to make the list contain no repeated elements, Bimal wishes to maximize the number of turns. If Amal and Bimal act optimally, we have to find how many turns are needed for this game. So, if the ...
Read MoreProgram to make target by removing from first or last and inserting again in Python
In this problem, we have two strings S and T that are permutations of each other. We can perform an operation where we remove either the first or last character from S and insert it anywhere in the string. The goal is to find the minimum number of operations needed to convert S into T. Problem Understanding Given strings s = "zyvxw" and t = "vwxyz", we need to transform s into t using the allowed operations. The key insight is to find the longest common subsequence that appears in the same order in both strings, then calculate ...
Read MoreProgram to delete all leaves with even values from a binary tree in Python
Suppose we have a binary tree, we will repeatedly delete all leaves that have even values. After deleting all even-valued leaves, if only the root remains and it has an even value, that will be deleted as well. So, if the input is like ? 13 12 14 16 22 ...
Read MoreProgram to find number of ways we can decode a message in Python
Suppose we have a mapping like a = 1, b = 2, ... z = 26, and we have an encoded message string. We need to count the number of ways it can be decoded using dynamic programming. For example, if the input is message = "222", then the output will be 3, as this can be decoded in 3 ways: "bbb" (2-2-2), "bv" (2-22), and "vb" (22-2). Algorithm To solve this problem, we will follow these steps − Create a memo array of size message length + 1 initialized with zeros Set memo[0] = ...
Read MoreProgram to check two parts of a string are palindrome or not in Python
Suppose we have two strings S and T of same length, we have to check whether it is possible to cut both strings at a common point so that the first part of S and the second part of T form a palindrome. So, if the input is like S = "cat" T = "dac", then the output will be True, as if we cut the strings into "c" + "at" and "d" + "ac", then "c" + "ac" is a palindrome. Algorithm To solve this, we will follow these steps − ...
Read MoreProgram to check whether we can take all courses or not in Python
Suppose we have a 2D matrix where matrix[i] represents the list of prerequisite courses needed to enroll in course i. We need to check whether it is possible to take all courses without encountering circular dependencies. So, if the input is like matrix = [[1], [2], []], then the output will be True, as we can take course 2, then course 1, and then course 0. Algorithm Overview This problem is essentially detecting cycles in a directed graph. We use Depth-First Search (DFS) with two tracking arrays: vis − tracks nodes currently in the DFS ...
Read MoreProgram to find a sublist where first and last values are same in Python
Suppose we have a list of numbers called nums, we have to find the number of sublists where the first element and the last element are same. So, if the input is like nums = [10, 15, 13, 10], then the output will be 5, as the sublists with same first and last element are: [10], [15], [13], [10], [10, 15, 13, 10]. Algorithm To solve this, we will follow these steps − num_sublists := size of nums d := an empty map for each n ...
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