Array Slicing

Array slicing involves taking a subset from an array and allocating a new array with those elements.

In Java you can create a new array of the elements in myArray, from startIndex to endIndex (exclusive), like this:

  Arrays.copyOfRange(myArray, startIndex, endIndex);

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Careful: there's a hidden time and space cost here! It's tempting to think of slicing as just "getting elements," but in reality you are:

This takes $O(n)$ time and $O(n)$ space, where $n$ is the number of elements in the resulting array.

That's a bit easier to see when you save the result of the slice to a variable:

  int[] tailOfArray = Arrays.copyOfRange(myArray, 1, myArray.length);

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But a bit harder to see when you don't save the result of the slice to a variable:

  return Arrays.copyOfRange(myArray, 1, myArray.length);
// whoops, I just spent O(n) time and space!

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  for (int item : Arrays.copyOfRange(myArray, 1, myArray.length)) {
    // whoops, I just spent O(n) time and space!
}

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So keep an eye out. Slice wisely.

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