## Positive AND codechef October long challenge Solution |Codechef October long challenge editorial -

This Problem is taken from Codechef  October long challenge and I have explained Positive and complete solution.

### Problem Statement-

A permutation ${p}_{1},{p}_{2}...{p}_{N}$ of $\left\{1,2,...,N\right\}$ is beautiful if ${p}_{i}\mathrm{&}{p}_{i+1}$ is greater than 0 for every $1\le i . You are given an integer $N$, and your task is toconstruct a beautiful permutation of length $N$ or determine that it's impossible.

Note that $a\mathrm{&}b$ denotes the bitwise AND of $a$ and $b$.

### Input:

First-line will contain $T$, number of testcases. Then the testcases follow. Each testcase contains a single line of input, an integer $N$.

### Output:

For each test case output $-1$ if there is no suitable permutation of length $N$, otherwise output $N$ integers in a single line which form a beautiful permutation. If there are multiple answers output any of them.

### Constraints

• $1\le N\le {10}^{5}$
• The sum of $N$ over all test cases does not exceed ${10}^{6}$

• 50 points : $1\le N,T\le 9$
• 50 points : Original constraints

### Sample Input:

3
4
3
5


### Sample Output:

-1
1 3 2
2 3 1 5 4


## link of problem-https://www.codechef.com/OCT20B/problems/POSANDRead More-Chef and Easy Queries CodeChef October long challenge problem solution editorialread more-Covid Run Codechef October long challenge problem solution| Codechef October long challenge problem solutionread More-Replace for X codechef October long challenge solution | codechef October long challenge editorial

### Solution-

Positive AND problem was little bit tricky problem.
mistake 1- Do not try to build the same output as given in custom input.
mistake 2- these can more then one ans of this problem so you can print any one of them.

I was thinking while solving the problem what wrong with the given permutation why it is not valid solution.
so i got ans by the observation that when a 2^n(1,2,4,8,16....) number AND with 2^n-1(1,3,7,15) number it forms always zero because in 2^n number only MSB present(eg 2=10,4=100,8=1000) other bit are equals to zero.
So my assumed permutation can be valid answer if i swap 2^n number with there next elements. so that it can not form 0 while doing AND
operation.
To make my permutation valid I have to swap these numbers with to number next to it. For eg. I will swap 8 to 9,16 to 17 ,32 to 33...
and print -1 if N is 2^n because in this case we cannot swap N to N+1 because we have no choice left.

So here is my working code.

### Vaccine Distribution Codechef December Long challenge solution 2020

Vaccine Distribution  Codechef December Long challenge solution 2020- This Problem vaccine distribution is taken from December long challenge 2020. lets read problem statement. Problem statement- Finally, a COVID vaccine is out on the market and the Chefland government has asked you to form a plan to distribute it to the public as soon as possible. There are a total of  N N  people with ages  a 1 , a 2 , … , a N a 1 , a 2 , … , a N . There is only one hospital where vaccination is done and it is only possible to vaccinate up to  D D  people per day. Anyone whose age is  ≥ 80 ≥ 80  or  ≤ 9 ≤ 9  is considered to be  at risk . On each day, you may not vaccinate both a person who is at risk and a person who is not at risk. Find the smallest number of days needed to vaccinate everyone. Input The first line of the input contains a single integer  T T  denoting the number of test cases. The description of  T T  test cases follows. The first line of each test case contains two space-separ

### Codechef February long challenge solution 2021

Codechef February  long challenge solution 2021- Hey guys Welcome Again, A small update CodeChef February  long challenge solution 2021 starting from 1st week of beb  2021 . Codechef long challenge is one of the popular contests of CodeChef you should participate in codechef Feb  long challenge.This is first contest of codechef in 2021 so good luck. And wish you happy new year. Contest link- https://www.codechef.com/FEB21/?itm_medium=navmenu&itm_campaign=FEB21 I will post the solution after Contest.Stay tuned. About CodeChef  February  long challenge solution 2021: CodeChef Long Challenge is a 10-day monthly coding contest where you can show off your computer programming skills. The significance being - it gives you enough time to think about a problem, try different ways of attacking the problem, read the concepts etc. If you’re usually slow at solving problems and have ample time at hand, this is ideal for you. We also put in a lot of efforts in getting quality problems, w

### Merge Two sorted array Without Extra Space

Problem statement-  Given two sorted arrays arr1[] and arr2[] of sizes N and M in non-decreasing order. Merge them in sorted order without using any extra space. Modify arr1 so that it contains the first N elements and modify arr2 so that it contains the last M elements.    Example 1: Input:  N = 4, arr1[] = [1 3 5 7]  M = 5, arr2[] = [0 2 6 8 9] Output:  arr1[] = [0 1 2 3] arr2[] = [5 6 7 8 9] Explanation: After merging the two  non-decreasing arrays, we get,  0 1 2 3 5 6 7 8 9.   Example 2: Input:  N = 2, arr1[] = [10, 12]  M = 3, arr2[] = [5 18 20] Output:  arr1[] = [5 10] arr2[] = [12 18 20] Explanation: After merging two sorted arrays  we get 5 10 12 18 20. Your Task: You don't need to read input or print anything. You only need to complete the function merge() that takes arr1, arr2, N and M as input parameters and modifies them in-place so that they look like the sorted merged array when concatenated. Expected Time Complexity:  O((n+m) log(n+m)) Expected Auxilliary Space: O(1