HeapDict.py

"""
Copyright 2009 Stutzbach Enterprises, LLC (daniel@stutzbachenterprises.com)

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

   1. Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
   2. Redistributions in binary form must reproduce the above
      copyright notice, this list of conditions and the following
      disclaimer in the documentation and/or other materials provided
      with the distribution.
   3. The name of the author may not be used to endorse or promote
      products derived from this software without specific prior written
      permission.

THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT,
INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE.
"""


import collections


def doc(s):
    if hasattr(s, '__call__'):
        s = s.__doc__

    def f(g):
        g.__doc__ = s
        return g

    return f


class heapdict(collections.MutableMapping):
    __marker = object()

    @staticmethod
    def _parent(i):
        return ((i - 1) >> 1)

    @staticmethod
    def _left(i):
        return ((i << 1) + 1)

    @staticmethod
    def _right(i):
        return ((i + 1) << 1)

    def __init__(self, *args, **kw):
        self.heap = []
        self.d = {}
        self.update(*args, **kw)

    @doc(dict.clear)
    def clear(self):
        del self.heap[:]
        self.d.clear()

    @doc(dict.__setitem__)
    def __setitem__(self, key, value):
        if key in self.d:
            self.pop(key)
        wrapper = [value, key, len(self)]
        self.d[key] = wrapper
        self.heap.append(wrapper)
        self._decrease_key(len(self.heap) - 1)

    def _min_heapify(self, i):
        l = self._left(i)
        r = self._right(i)
        n = len(self.heap)
        if l < n and self.heap[l][0] < self.heap[i][0]:
            low = l
        else:
            low = i
        if r < n and self.heap[r][0] < self.heap[low][0]:
            low = r

        if low != i:
            self._swap(i, low)
            self._min_heapify(low)

    def _decrease_key(self, i):
        while i:
            parent = self._parent(i)
            if self.heap[parent][0] < self.heap[i][0]: break
            self._swap(i, parent)
            i = parent

    def _swap(self, i, j):
        self.heap[i], self.heap[j] = self.heap[j], self.heap[i]
        self.heap[i][2] = i
        self.heap[j][2] = j

    @doc(dict.__delitem__)
    def __delitem__(self, key):
        wrapper = self.d[key]
        while wrapper[2]:
            parentpos = self._parent(wrapper[2])
            parent = self.heap[parentpos]
            self._swap(wrapper[2], parent[2])
        self.popitem()

    @doc(dict.__getitem__)
    def __getitem__(self, key):
        return self.d[key][0]

    @doc(dict.__iter__)
    def __iter__(self):
        return iter(self.d)

    def popitem(self):
        """D.popitem() -> (k, v), remove and return the (key, value) pair with lowest\nvalue; but raise KeyError if D is empty."""
        wrapper = self.heap[0]
        if len(self.heap) == 1:
            self.heap.pop()
        else:
            self.heap[0] = self.heap.pop(-1)
            self.heap[0][2] = 0
            self._min_heapify(0)
        del self.d[wrapper[1]]
        return wrapper[1], wrapper[0]

    @doc(dict.__len__)
    def __len__(self):
        return len(self.d)

    def peekitem(self):
        """D.peekitem() -> (k, v), return the (key, value) pair with lowest value;\n but raise KeyError if D is empty."""
        return (self.heap[0][1], self.heap[0][0])


del doc
__all__ = ['heapdict']