99 lines
2.1 KiB
Lua
99 lines
2.1 KiB
Lua
--------------------------------------------------------------------------------
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--- Queue of objects sorted by priority
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-- @module lua-nucleo.priority_queue
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-- This file is a part of lua-nucleo library
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-- @copyright lua-nucleo authors (see file `COPYRIGHT` for the license)
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--------------------------------------------------------------------------------
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local arguments,
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method_arguments
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= import 'lua-nucleo/args.lua'
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{
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'arguments',
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'method_arguments'
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}
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local lower_bound_gt
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= import 'lua-nucleo/algorithm.lua'
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{
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'lower_bound_gt'
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}
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--------------------------------------------------------------------------------
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local table_insert, table_remove = table.insert, table.remove
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--------------------------------------------------------------------------------
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--- Priority Queue
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-- @factory priority_queue
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local make_priority_queue
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do
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local PRIORITY_KEY = 1
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local VALUE_KEY = 2
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local insert = function(self, priority, value)
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method_arguments(
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self,
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"number", priority
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)
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assert(value ~= nil, "value can't be nil") -- value may be of any type, except nil
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local queue = self.queue_
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local k = lower_bound_gt(queue, PRIORITY_KEY, priority)
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table_insert(queue, k, { [PRIORITY_KEY] = priority, [VALUE_KEY] = value })
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end
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local front = function(self)
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method_arguments(
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self
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)
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local queue = self.queue_
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local front_elem = queue[#queue]
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if front_elem == nil then
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return nil
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end
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return front_elem[PRIORITY_KEY], front_elem[VALUE_KEY]
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end
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--- pop last value.
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-- @return priority
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-- @return value
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local pop = function(self)
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method_arguments(
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self
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)
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local front_elem = table_remove(self.queue_)
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if front_elem == nil then
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return nil
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end
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return front_elem[PRIORITY_KEY], front_elem[VALUE_KEY]
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end
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--- construct a `priority_queue`.
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-- @constructor
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make_priority_queue = function()
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--- @export
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return
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{
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insert = insert;
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front = front;
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pop = pop;
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--
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queue_ = { };
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}
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end
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end
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return
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{
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make_priority_queue = make_priority_queue;
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}
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