Solved Problem - Reverse Subarray

In this lesson, we'll discuss a solved problem about how to reverse the given subarray of an array.

Problem statement

Given an array AA of NN integers. Answer QQ queries of the type (l,r)(l, r) - reverse the subarray A[l...r]A[l...r]. Print the array after each query.

Input format The first line contains two integers NN and QQ (1N,Q103)(1 \leq N, Q \leq 10^3).

The second line contains NN space-separated integers representing the array A[]A[] (1A[i]106)(1 \leq A[i] \leq 10^6).

Next, QQ lines each contains pair of integers ll and rr (1lrN)(1 \leq l \leq r \leq N).


Sample

Input

5 3
1 2 3 4 5
1 5
2 3
3 5

Output

5 4 3 2 1
5 3 4 2 1
5 3 1 2 4

Solution

For each query, we can reverse the given array in O(N)O(N) time. Let’s see how we would reverse the entire array; we can then do the same to reverse a subarray.

We start with two pointers, one at the start and one at the end of the array. Pointer 1 moves to the right and Pointer 2 moves to the left after each step. At each step, we swap the elements at the two pointers.

See the below illustrations for better understanding.

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