edaBit-coding-challenges/Josephus-Permutation

Josephus Permutation

by Matt tags: loops, recursion, math

Summary

A group of n prisoners stand in a circle awaiting execution. Starting from an arbitrary position(0), the executioner kills every kth person until one person remains standing, who is then granted freedom (see examples). Create a function that takes 2 arguments — the number of people to be executed n, and the step size k, and returns the original position (inde

Instructions

A group of n prisoners stand in a circle awaiting execution. Starting from an arbitrary position(0), the executioner kills every kth person until one person remains standing, who is then granted freedom (see examples).

Create a function that takes 2 arguments — the number of people to be executed n, and the step size k, and returns the original position (index) of the person who survives.

Examples

whoGoesFree(9, 2) ➞ 2

// Prisoners = [0, 1, 2, 3, 4, 5, 6, 7, 8]
// Executed people replaced by - (a dash) for illustration purposes.
// 1st round of execution = [0, -, 2, -, 4, -, 6, -, 8]  -> [0, 2, 4, 6, 8]
// 2nd round = [-, 2, -, 6, -] -> [2, 6]  # 0 is killed in this round because it's beside 8 who was skipped over.
// 3rd round = [2, -]

whoGoesFree(9, 3) ➞ 0

// [0, 1, 2, 3, 4, 5, 6, 7, 8]
// [0, 1, -, 3, 4, -, 6, 7, -] -> [0, 1, 3, 4, 6, 7]
// [0, 1, -, 4, 6, -] -> [0, 1, 4, 6]
// [0, 1, -, 6] -> [0, 1, 6]
// [0, -, 6] -> [0, 6]
// [0, -] -> [0]

Notes

Refer to Resources tab for more info.