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added flow - part
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tieskedh
tieskedh
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flow

The if-else if-else chain can be reduced to two if-statements.
This is because the case where the absolute value of cur and prev are the same is just the other two cases combined.
As far as I know, you do need more variables, to make it possible. Therefor, this is just another choice, with its own drawbacks:

fun asteroidCollision(asteroids: IntArray): IntArray { val stack = asteroids.toMutableList() var index = stack.lastIndex while (index >= 1) { val curIndex = index val cur = stack[curIndex] val prevIndex = index-1 val prev = stack[prevIndex] if (prev.isRight() && cur.isLeft()) { if (abs(prev) >= abs(cur)){ stack.removeAt(curIndex) if (index-1==stack.lastIndex) index-- } if (abs(cur) <= abs(prev)){ stack.removeAt(prevIndex) index-- } } else index-- } return stack.toIntArray() }

flow

The if-else if-else chain can be reduced to two if-statements.
This is because the case where the absolute value of cur and prev are the same is just the other two cases combined.
As far as I know, you do need more variables, to make it possible. Therefor, this is just another choice, with its own drawbacks:

fun asteroidCollision(asteroids: IntArray): IntArray { val stack = asteroids.toMutableList() var index = stack.lastIndex while (index >= 1) { val curIndex = index val cur = stack[curIndex] val prevIndex = index-1 val prev = stack[prevIndex] if (prev.isRight() && cur.isLeft()) { if (abs(prev) >= abs(cur)){ stack.removeAt(curIndex) if (index-1==stack.lastIndex) index-- } if (abs(cur) <= abs(prev)){ stack.removeAt(prevIndex) index-- } } else index-- } return stack.toIntArray() }
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tieskedh
tieskedh
  • 842
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  • 14

An array to list can be done by the function toList().
list.size-1 is an existing property on a list called lastIndex.

'Math.abs' is from Java. Kotlin has its own abs, which isn't prefixed by a class.

List provides an operator function to access by index: stack.get(curIndex) can be written as stack[curIndex]

fun asteroidCollision(asteroids: IntArray): IntArray { val stack = asteroids.toMutableList() var curIndex = stack.lastIndex while (curIndex >= 1) { val cur = stack[curIndex] val prev = stack[curIndex - 1] if (prev.isRight() && cur.isLeft()) { if (abs(cur) == abs(prev)) { stack.removeAt(curIndex) stack.removeAt(curIndex - 1) if (curIndex - 2 == stack.lastIndex) curIndex -= 2 else curIndex-- } else if (abs(prev) > abs(cur)) { stack.removeAt(curIndex) if (curIndex - 1 == stack.lastIndex) curIndex-- } else { stack.removeAt(curIndex - 1) curIndex-- } } else curIndex-- } return stack.toIntArray() }