SDE - 1

You are given ‘N’ pairs of integers in which the first number is always smaller than the second number i.e in pair (a,b) -> a < b always. Now we define a pair chain as the continuous arrangement of pairs in which a pair (c,d) can follow another pair (a,b) only when b < c.

Find the length of the longest pair chain that can be formed using the given pairs.

Example:

Given Pairs =  [3,4], [1,2], [2,3].

The length of the maximum chain will be 2. The longest chain is [1,2] -> [3,4].

Note:

1. You can select a pair only once.

2. You needn’t use up all the given pairs.

3. You can select pairs in any order. 

Alex has a list of items to purchase at a market. The cashier offers to discount the items after the first one by the lowest marked price among the prior items. No item's price can be discounted below 0, and the items cannot be reordered. Calculate the payable amount.Example: prices = [2,5,1,4]Alex pays 2 for the first item,Second item costs, 5 - 2 = 3Third item costs, max(1 - min(5, 2), 0) = 0Fourth item costs, 4 - 1 = 3

Questions on semaphores, mutex, polling, TCP servers, load balancing and DNS

Given a binary tree. Find and return the modulus of the difference between the sum of odd level nodes and the sum of even level nodes.

Questions on sharding and partitioning

You have been given a permutation of ‘N’ integers. A sequence of ‘N’ integers is called a permutation if it contains all integers from 1 to ‘N’ exactly once. Your task is to rearrange the numbers and generate the lexicographically next greater permutation.

To determine which of the two permutations is lexicographically smaller, we compare their first elements of both permutations. If they are equal — compare the second, and so on. If we have two permutations X and Y, then X is lexicographically smaller if X[i] < Y[i], where ‘i’ is the first index in which the permutations X and Y differ.

For example, [2, 1, 3, 4] is lexicographically smaller than [2, 1, 4, 3].

You are given an array consisting of N positive integers, and your task is to sort the array in decreasing order of count of set bits in the binary representation of the integers present in the array.

In other words, you have to modify the array such that an integer with more number of set bits should appear before the integer which has lesser number of set bits in its binary representation.

The number of set bits is nothing but the number of 1s present in the binary representation of the integer. For example, the number of set bits in 5(0101) is equal to 2.

Note :

1. If any two numbers have the same count of set bits, then in the sorted array they will appear in the order in which they appear in the original array. For example, let the array be { 2, 4, 3}, in this case, both 2 and 4 have the same number of set bits so the answer will be {3, 2, 4} and not {3, 4, 2}, because in the original array 2 appears before 4.

2. The array may contain duplicate elements.

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What is a singleton class?

How to design a singleton class?

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