## Problem Statement

A class has **N** number of students. When the students submit an assignment, they are assigned **K** peers to review their assignments and provide feedback such that *0 < K = N*

#### Example:

*Input:* N=3, K=1

*Output:*

{ 0: [1], 1: [2], 2: [0] }

*Input:* N=3, K=2

{ 0: [1,2], 1: [2,0], 2: [0,1] }

## Solution

def generate_peer_pairs(N, K): """A function that provides unique peers for reviewing. The generated matches follow the following rules: 1. The no.of reviews/rounds of review is less than total no.of users. 2. The user won't be reviewing his/her own work 3. All the reviewers assigned would be unique. 4. Each user will have equal no.of reviews to give and receive. :param N: Total no.of student for whom the matching is to be done. :param K: The no.of reviews each student is supposed to receive. :returns: a dictionary of graders and their peers { grader_id: [peer_1, peer_2, ...]} """ if K >= N: return False available_offsets = list(range(1, N)) offsets = [] while len(offsets) < rounds: offset = random.choice(available_offsets) offsets.append(offset) available_offsets.remove(offset) students = list(range(N)) random.shuffle(students) allocations = {} for idx, student in enumerate(students): allocations[student] = [students[(idx + offset) % N] for offset in offsets]) return allocations

## Notes

The problem is an interesting one. I started out with the idea that the peers should be arranged in a random way and wrote an algorithm by selecting a random recipient while looping over each grader. It was completely non-roboust and failed to make the right pairs more times that it worked.

The solution if you had noticed, is completely a position shifting algorithm. What appears a non-repeating random order for the grader and the recipient is not really that random.