You could utilize enumerate, zip and list comprehensions: >>> a = [0, 4, 10, 100] # basic enumerate without condition: >>> [x – a[i – 1] for i, x in enumerate(a)][1:] [4, 6, 90] # enumerate with conditional inside the list comprehension: >>> [x – a[i – 1] for i, x in enumerate(a) if i … Read more
def pairs(lst): i = iter(lst) first = prev = item = i.next() for item in i: yield prev, item prev = item yield item, first Works on any non-empty sequence, no indexing required.
Its a bit tricky – the sum() function takes the start and adds it to the next and so on You need to implement the __radd__ method: class T: def __init__(self,x): self.x = x def __radd__(self, other): return other + self.x test = (T(1),T(2),T(3),200) print sum(test)
LinkedList might allocate fewer entries, but those entries are astronomically more expensive than they’d be for ArrayList — enough that even the worst-case ArrayList is cheaper as far as memory is concerned. (FYI, I think you’ve got it wrong; ArrayList grows by 1.5x when it’s full, not 2x.) See e.g. https://github.com/DimitrisAndreou/memory-measurer/blob/master/ElementCostInDataStructures.txt : LinkedList consumes 24 … Read more
The main thing to be concerned about is what other code might have a reference to the list. If the existing list is visible elsewhere, do you want that code to see a cleared list, or keep the existing one? If nothing else can see the list, I’d probably just clear it – but not … Read more
That’s because num is a Char, i.e. the resulting values are the ascii value of that char. This will do the trick: val txt = “82389235” val numbers = txt.map { it.toString().toInt() } The map could be further simplified: map(Character::getNumericValue)
You are likely importing java.awt.List. You should instead import java.util.List, which is a parameterized type.
Retrieving an element by index is an O(n) operation for linked list, which is what std::list is. So it was decided that providing operator[] would be deceptive, since people would be tempted to actively use it, and then you’d see code like: std::list<int> xs; for (int i = 0; i < xs.size(); ++i) { int … Read more
[input[i:i+n] for i in range(0, len(input), n)] # Use xrange in py2k where n is the length of a chunk. Since you don’t define what might happen to the final element of the new list when the number of elements in input is not divisible by n, I assumed that it’s of no importance: with … Read more
Recently I wrote a small library called StreamEx which extends Java streams and provides this exact method among many other features: StreamEx.of(-2,1,2,-5) .filter(n -> n > 0) .map(n -> n * n) .toList(); Also toSet(), toCollection(Supplier), joining(), groupingBy() and other shortcut methods are available there.