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feat: add new Josephus file in Recursive directory #1728
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,25 @@ | ||
| /** | ||
| * @function Josephus | ||
| * @description recursive implementation of the Josephus function. | ||
| * @param {Integer[]} collection - The integer array. | ||
| * @param {Integer} - The step size. | ||
| * @return {Integer} - The last integer in the list. | ||
| * @see [JosephusProblem](https://en.wikipedia.org/wiki/Josephus_problem) | ||
| * @example [1,2,3,4,5,6,7] with step 3 = 4 | ||
| */ | ||
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| const josephus = (collection, step) => { | ||
| // return null for invalid steps that are less than or equal to 0 | ||
| if (step <= 0 || collection.length === 0) { | ||
| return null | ||
| } | ||
| if (collection.length === 1) { | ||
| return collection[0] | ||
| } else { | ||
| step = (step - 1) % collection.length | ||
| collection.splice(step, 1) | ||
|
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. This is This algorithm also doesn't really benefit from recursion. It would be clearer as a simple while (collection.length > 1) { /* kill someone */ } return collection[0] |
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| return josephus(collection, step + collection.length) | ||
| } | ||
| } | ||
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| export { josephus } | ||
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,40 @@ | ||
| import { josephus } from '../Josephus' | ||
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| describe('Josephus', () => { | ||
| const collection = [1, 2, 3, 4, 5, 6, 7] | ||
| const collection1 = [1] | ||
| const collection2 = [] | ||
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| it('should return 4 for step size of 3', () => { | ||
|
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Repetitive tests of the form "should return X for Y" should use |
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| const step = 3 | ||
| expect(josephus([...collection], step)).toBe(4) | ||
| }) | ||
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| it('should return 4 for a step size of 10', () => { | ||
| const step = 10 | ||
| expect(josephus([...collection], step)).toBe(4) | ||
| }) | ||
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| it('should return null for a step size of 0 as it is invalid', () => { | ||
| const step = 0 | ||
| expect(josephus([...collection], step)).toBeNull() | ||
| }) | ||
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| it('should return 7 for a step size of 1000', () => { | ||
| const step = 1000 | ||
| expect(josephus([...collection], step)).toBe(7) | ||
| }) | ||
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| it('should return null for a step size of -1 as it is invalid', () => { | ||
| const step = -1 | ||
| expect(josephus([...collection], step)).toBeNull() | ||
| }) | ||
| it('should return 1 for a collection with just 1', () => { | ||
| const step = 2 | ||
| expect(josephus([...collection1], step)).toBe(1) | ||
| }) | ||
| it('should return null for an empty collection as it is invalid', () => { | ||
| const step = 3 | ||
| expect(josephus([...collection2], step)).toBeNull() | ||
| }) | ||
| }) | ||