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Technical articles with clear explanations and examples

Minimum Cost For Tickets in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 629 Views

Suppose there is a country, that is popular for train travel, we have planned some train travelling one year in advance. We have an array, that is holding the days of the year that we will travel. Each day is an integer from 1 to 365. Train tickets are sold in three different ways −A 1-day pass is sold for costs[0] dollars;A 1-day pass is sold for costs[0] dollars;A 30-day pass is sold for costs[2] dollars.Here the passes allow that many days of consecutive travel. For example, if we get one 7-day pass on day 2, then we can travel ...

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Find Smallest Common Element in All Rows in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 385 Views

Suppose we have a matrix mat where every row is sorted in non-decreasing order, we have to find the smallest common element in all rows. If there is no common element, then return -1. So if the matrix is like −1234524581035791113579The output will be 5To solve this, we will follow these steps −Define a map m, n := row count of matrix, if n is not 0, then x = column size, otherwise 0for i in range 0 to n – 1for j in range 0 to x – 1if m[mat[i, j]] + 1 = i + 1, then increase ...

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XOR of all elements of array with set bits equal to K in C++

sudhir sharma
sudhir sharma
Updated on 11-Mar-2026 410 Views

In this problem, we are given an array of n elements and an integer value k. Our task is to find XOR of all elements of the array that have set bits equal to k.Let’s take an example to understand the problem, Inputarray = {2, 12, 44, 103, 17} , K =3Output44To solve this problem, we will count set bit of every element of the array and compare it with k. If the number of set bits is equal to k, then we will push it to a vector and find XOR of all elements of the vector.For finding the ...

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Number of Subarrays with Bounded Maximum in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 309 Views

Suppose we have an array A of positive integers, and two positive integers L and R are also given. We have to find the number of (contiguous, non-empty) subarrays such that the value of the maximum array element in that subarray is at least L and at most R. So if A = [2, 1, 4, 3] and L = 2 and R = 3, then output will be 3 as there are three sub arrays that meet the requirements. So these are [2], [2, 1], [3].To solve this, we will follow these steps −ret := 0, dp := 0, ...

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Ugly Number III in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 359 Views

Suppose we have to write a program to find the n-th ugly number. The Ugly numbers are positive integers which are divisible by a or b or c. So for example, if n = 3 and a = 2, b = 3 and c = 5, then the output will be 4, as the ugly numbers are [2, 3, 4, 5, 6, 8, 9, 10], the third one is 4.To solve this, we will follow these steps −make a method called ok(), this will take x, a, b, c, this will act like below −return (x/a) + (x/b) + (x/c) ...

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All Paths From Source to Target in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 620 Views

Suppose we have a directed, acyclic graph with N nodes. We have to find all possible paths from node 0 to node N-1, and return them in any order. The graph is given as follows: the nodes are 0, 1, ..., graph.length - 1. graph[i] is a list of all nodes j for which the edge (i, j) exists.So if the input is like [[1, 2], [3], [3], []], then the output will be [[0, 1, 3], [0, 2, 3]].To solve this, we will follow these steps −Make one 2d array called resDefine a method called solve, this will take ...

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XOR of a submatrix queries in C++

sudhir sharma
sudhir sharma
Updated on 11-Mar-2026 291 Views

In this problem, we are given a N x N matrix and some queries, each query contains the top-left and bottom-right corner of the submatrix created from this matrix. Our task is to find the XOR of all elements of the submatrix defined by the querries.Let’s take an example to understand the problem, Inputarr[][] = {{1, 2, 3} {4, 5, 6} {7, 8, 9}} Querries: {0, 0, 1, 2} , {1, 2, 2, 2}Output1 15Explainationquerry 1 : 1^2^3^4^5^6 querry 2 : 6^9To solve this problem, we will find a prefix-XOR matrix to solve queries. The value of the matrix at ...

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Minimum Swaps To Make Sequences Increasing in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 483 Views

Suppose we have two integer sequences A and B of the same non-zero length. We can swap elements A[i] and B[i]. We have to keep in mind that both elements are in the same index position in their respective sequences. After completing some number of swaps, A and B are both strictly increasing. We have to find the minimum number of swaps to make both sequences strictly increasing.So if the input is like A = [1, 3, 5, 4] and B = [1, 2, 3, 7], then the answer will be 1, if we swap A[3] with B[3], then the ...

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Maximum Binary Tree II in C++

Arnab Chakraborty
Arnab Chakraborty
Updated on 11-Mar-2026 303 Views

Suppose we have a root node of a maximum tree: The maximum tree is a tree where every node has a value greater than any other value in its subtree. Suppose we have a method called construct(). This can construct a root from a list A. The construct() method is like −If list A is empty, return null.Otherwise, let A[i] be the largest element of the list A. Then create a root node with value A[i].The left child of root will be construct([A[0], A[1], ..., A[i-1]])The right child of root will be construct([A[i+1], A[i+2], ..., A[n - 1]]) [n is ...

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XOR of a subarray in C++

sudhir sharma
sudhir sharma
Updated on 11-Mar-2026 255 Views

In this problem, we are given an arr[] and some queries that are range between L to R in the array. Our task is to print the XOR of the subarray between L to R.Let’s take an example to understand the problem, Input − array = {1, 4, 5, 7, 2, 9} L = 1 , R = 5Output −Explanation − 4^5^7^2^9To solve this problem, we will create an array, based on the following observation, We will XOR multiple bits, if there are odd number of 1s, the result will be 1 otherwise the result is 0.Now, we will create ...

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