codon/stdlib/sortedlist.codon

# Copyright (C) 2022 Exaloop Inc. <https://exaloop.io>

from bisect import bisect_right, bisect_left, insort
from collections import deque

DEFAULT_LOAD_FACTOR = 1000

class SortedList:
    _len: int
    _load: int
    _lists: List[List[T]]
    _maxes: List[T]
    _offset: int
    T: type

    def __init__(self):
        self._len = 0
        self._load = DEFAULT_LOAD_FACTOR
        self._lists = []
        self._maxes = []
        self._offset = 0

    def clear(self):
        """
        Remove all values from sorted list.
        Runtime complexity: `O(n)`
        """
        self._len = 0
        self._lists.clear()
        self._maxes.clear()
        self._offset = 0

    @property
    def left(self) -> T:
        if not self._lists:
            raise IndexError("list index out of range")
        return self._lists[0][0]

    def add(self, value: T):
        """
        Add `value` to sorted list.
        Runtime complexity: `O(log(n))` -- approximate.
        >>> sl = SortedList()
        >>> sl.add(3)
        >>> sl.add(1)
        >>> sl.add(2)
        >>> sl
        SortedList([1, 2, 3])
        :param value: value to add to sorted list
        """
        if self._maxes:
            pos = bisect_right(self._maxes, value)
            if pos == len(self._maxes):
                pos -= 1
                self._lists[pos].append(value)
                self._maxes[pos] = value
            else:
                insort(self._lists[pos], value)
            self._expand(pos)
        else:
            self._lists.append([value])
            self._maxes.append(value)
        self._len += 1

    def _expand(self, pos: int):
        """
        Split sublists with length greater than double the load-factor.
        Updates the index when the sublist length is less than double the load
        level. This requires incrementing the nodes in a traversal from the
        leaf node to the root. For an example traversal see
        ``SortedList._loc``.
        """
        if len(self._lists[pos]) > (self._load << 1):
            _maxes = self._maxes

            _lists_pos = self._lists[pos]
            half = _lists_pos[self._load :]
            del _lists_pos[self._load :]
            _maxes[pos] = _lists_pos[-1]

            self._lists.insert(pos + 1, half)
            _maxes.insert(pos + 1, half[-1])

    def _delete(self, pos: int, idx: int):
        """
        Delete value at the given `(pos, idx)`.
        Combines lists that are less than half the load level.
        Updates the index when the sublist length is more than half the load
        level. This requires decrementing the nodes in a traversal from the
        leaf node to the root. For an example traversal see
        ``SortedList._loc``.
        :param int pos: lists index
        :param int idx: sublist index
        """
        _lists_pos = self._lists[pos]
        del _lists_pos[idx]
        self._len -= 1

        len_lists_pos = len(_lists_pos)

        if len_lists_pos > (self._load >> 1):
            self._maxes[pos] = _lists_pos[-1]
        elif len(self._lists) > 1:
            if not pos:
                pos += 1

            prev = pos - 1
            self._lists[prev].extend(self._lists[pos])
            self._maxes[prev] = self._lists[prev][-1]

            del self._lists[pos]
            del self._maxes[pos]

            self._expand(prev)
        elif len_lists_pos:
            self._maxes[pos] = _lists_pos[-1]
        else:
            del self._lists[pos]
            del self._maxes[pos]

    def __iter__(self) -> Generator[T]:
        for l in self._lists:
            yield from l

    def __len__(self) -> int:
        return self._len

    def __bool__(self) -> bool:
        return self._len > 0