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Round-Robin is a way to rotate an array of items such that each item can be paired with every other item exactly once. In sports, this is a way to ensure that each team plays every other team exactly once.

Imagine you have an array of 10 teams, and each team has a number:

[1,2,3,4,5,6,7,8,9,10]

Your goal is to write a function that takes an input array and returns an array of arrays of arrays.

For example, for an array input of [1,2,3,4] the result would be:

[
  [           // ---- round 1 -----
    [1, 4],   // 1 plays 4
    [3, 2],   // 3 plays 2
  ],
  [           // ---- round 2 -----
    [1, 3],   // 1 plays 3
    [2, 4],   // 2 plays 4
  ],
  [           // ---- round 3 -----
    [1, 2],   // 1 plays 2
    [4, 3],   // 4 plays 3
  ]
]

1. Split the array in half
2. Reverse the second array

The result should look like this:

Take the first element of the first array, and match it with the first element of the second array, and so on. Visually, that looks like:

In code, that looks like:

[
  [1, 10],
  [2, 9 ],
  [3, 8 ],
  [4, 7 ],
  [5, 6 ],
]

• Keep the first element of the first array in its position (it will never change)
• Rotate the other numbers counter-clockwise

Which ends up looking like:

Take the first element of the first array, and match it with the first element of the second array, and so on. Visually, that looks like:

[
  [1,  9],
  [10, 8],
  [2,  7],
  [3,  6],
  [4,  5],
]

Your round robin function should never return duplicate matches.

You will be working in Jasmine to solve this problem.

Open index.html in a browser to see the tests run. As you make changes to your round robin js file, hit refresh (CMD+R) in your browser to run the tests again.

1. Install LoDash in index.html
2. Use LoDash Methods, write code to pass specs

In a separate file called ui.html create an HTML page that:

1. Loads up jQuery

• Can you load it from the CDN?
• From Bower?

1. Has a textarea where users can enter a list of teams, separated by newlines
2. Has a button that users can click to generate a schedule
3. When the button is clicked, print the schedule according to the wireframe
4. When the button is clicked again, clear the previous schedule, and recreate

NOTE: use custom CSS for this - no frameworks.

1. Create a copy of index.html
2. Remove the reference to LoDash
3. Create a new function roundRobinPure and solve it with pure JS

'nuff said.

• http://en.wikipedia.org/wiki/Round-robin_tournament#Scheduling_algorithm