2

Construct the Lexicographically Largest Valid Sequence

Difficulty: MEDIUM
Contributed By
Shrey Pansuria
Avg. time to solve
35 min
Success Rate
65%

Problem Statement

You are given a positive integer N. Your task is to create the lexicographically largest sequence of length 2*N - 1 containing integers between 1 to N such that:

1. 1 occurs in the sequence exactly once.
2. Each integer between 2 to N(inclusive) occurs in the sequence exactly twice.
3. For each integer i between 2 to N, the distance between the two occurrences of i should be exactly i.

Note:

1. A sequence A is lexicographically larger than a sequence B (of the same length), if in the first position where A and B differ, sequence A has a number greater than the corresponding number in B.
2. It is guaranteed that under the given constraints, there is always a solution. 
Input Format:
The first line contains an integer, ‘T’ which denotes the number of test cases or queries to be run. Then, the T test cases follow.

The first and the only line of each test case contains one integer N, as described in the problem statement.
Output Format:
For each test case, print in a new line, 2*'N' - 1 space-separated integer representing the lexicographically largest sequence for the given input.
Note:
You do not need to print anything. It has already been taken care of. Just implement the given function.
Constraints:
1 <= T <= 100
1 <= N <= 20

Time Limit: 1 second
Sample Input 1:
1
2
Sample Output 1:
2 1 2
Explanation Of Sample Input 1:
In test case 1: Since 1 occurs exactly once and 2 occurs exactly twice, and the distance between the two occurrences of 2 is 2. The sequence {2,1,2} is also the lexicographically largest sequence possible that satisfies the given condition.
Sample Input 2:
1
3
Sample Output 2:
3 1 2 3 2
Explanation Of Sample Input 2:
In test case 1: [3, 1, 2, 3, 2] is the largest lexicographically sequence which we need.
Reset Code
Full screen
copy-code
Console