SDE - 1

You are given a linked list containing N nodes where each node is associated with a certain value. Return a linked list as follows: If the input linked list is 1-->2-->3-->4, then the output should be 1-->4-->2-->3. And if the input is 1-->2-->3-->4-->5, then the output should be 1-->5-->2-->4-->3.

In other words, if the original linked list is first -> second -> third -> ……….->thirdlast -> secondlast -> last, then the modified linked list would be first -> last -> second -> second_last -> ...

Note

1. All the node values are positive.

2. The size of the linked list is greater than 1.

3. The end of the linked list is represented by -1.

You are given an array/list 'prices' where the elements of the array represent the prices of the stock as they were yesterday and indices of the array represent minutes. Your task is to find and return the maximum profit you can make by buying and selling the stock. You can buy and sell the stock only once.

Note:

You can’t sell without buying first.

For Example:

For the given array [ 2, 100, 150, 120],
The maximum profit can be achieved by buying the stock at minute 0 when its price is Rs. 2 and selling it at minute 2 when its price is Rs. 150.
So, the output will be 148.

You are given an array of integers 'ARR' of size 'N' and another integer 'K'.

Your task is to find and return 'K'th smallest value present in the array.

Note: All the elements in the array are distinct.

Example

If 'N' is 5 and 'K' is 3 and the array is 7, 2, 6, 1, 9

Sorting the array we get 1, 2, 6, 7, 9

Hence the 3rd smallest number is 6.

Aahad and Harshit always have fun by solving problems. Harshit took a sorted array consisting of distinct integers and rotated it clockwise by an unknown amount. For example, he took a sorted array = [1, 2, 3, 4, 5] and if he rotates it by 2, then the array becomes: [4, 5, 1, 2, 3].

After rotating a sorted array, Aahad needs to answer Q queries asked by Harshit, each of them is described by one integer Q[i]. which Harshit wanted him to search in the array. For each query, if he found it, he had to shout the index of the number, otherwise, he had to shout -1.

For each query, you have to complete the given method where 'key' denotes Q[i]. If the key exists in the array, return the index of the 'key', otherwise, return -1.

Note:

Can you solve each query in O(logN) ?

Difference b/w select_related and prefetch_related? (Learn)

You are given an integer ‘N’ which denotes a set of N people numbered from 1 to N and a matrix ‘DISLIKE’ with M rows and 2 columns. Each row in the matrix denotes two people who dislike each other i.e. for any valid row i, DISLIKE[i][0] dislikes DISLIKE[i][1] and vice versa.

Your task is to split the set of N people into two groups under the conditions:

1. It is not allowed to put two persons in the same group who dislike each other.

2. The size of the two groups may or may not be equal.

3. Each person from the set belongs to exactly one group.

You are given an array of integers ‘coins’ denoting the denomination of coins and another array of integers ‘freq’ denoting the number of coins of each denomination.

You have to find the number of ways to make the sum ‘V’ by selecting some(or all) coins from the array.

The answer can be very large. So, return the answer modulo 1000000007.

For Example :

‘N’ = 3, ‘coins’ = {1, 2, 3}, ‘freq’ = {1, 1, 3}, ‘V’ = 6

For the given example, we can make six by using the following coins:
{1, 2, 3}
{3. 3}
Hence, the answer is 2.

Design Instagram (Practice)