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| -rw-r--r-- | util/indexedbheap.lua | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/util/indexedbheap.lua b/util/indexedbheap.lua new file mode 100644 index 00000000..3cb03037 --- /dev/null +++ b/util/indexedbheap.lua @@ -0,0 +1,153 @@ + +local setmetatable = setmetatable; +local math_floor = math.floor; +local t_remove = table.remove; + +local function _heap_insert(self, item, sync, item2, index) + local pos = #self + 1; + while true do + local half_pos = math_floor(pos / 2); + if half_pos == 0 or item > self[half_pos] then break; end + self[pos] = self[half_pos]; + sync[pos] = sync[half_pos]; + index[sync[pos]] = pos; + pos = half_pos; + end + self[pos] = item; + sync[pos] = item2; + index[item2] = pos; +end + +local function _percolate_up(self, k, sync, index) + local tmp = self[k]; + local tmp_sync = sync[k]; + while k ~= 1 do + local parent = math_floor(k/2); + if tmp < self[parent] then break; end + self[k] = self[parent]; + sync[k] = sync[parent]; + index[sync[k]] = k; + k = parent; + end + self[k] = tmp; + sync[k] = tmp_sync; + index[tmp_sync] = k; + return k; +end + +local function _percolate_down(self, k, sync, index) + local tmp = self[k]; + local tmp_sync = sync[k]; + local size = #self; + local child = 2*k; + while 2*k <= size do + if child ~= size and self[child] > self[child + 1] then + child = child + 1; + end + if tmp > self[child] then + self[k] = self[child]; + sync[k] = sync[child]; + index[sync[k]] = k; + else + break; + end + + k = child; + child = 2*k; + end + self[k] = tmp; + sync[k] = tmp_sync; + index[tmp_sync] = k; + return k; +end + +local function _heap_pop(self, sync, index) + local size = #self; + if size == 0 then return nil; end + + local result = self[1]; + local result_sync = sync[1]; + index[result_sync] = nil; + if size == 1 then + self[1] = nil; + sync[1] = nil; + return result, result_sync; + end + self[1] = t_remove(self); + sync[1] = t_remove(sync); + index[sync[1]] = 1; + + _percolate_down(self, 1, sync, index); + + return result, result_sync; +end + +local indexed_heap = {}; + +function indexed_heap:insert(item, priority, id) + if id == nil then + id = self.current_id; + self.current_id = id + 1; + end + self.items[id] = item; + _heap_insert(self.priorities, priority, self.ids, id, self.index); + return id; +end +function indexed_heap:pop() + local priority, id = _heap_pop(self.priorities, self.ids, self.index); + if id then + local item = self.items[id]; + self.items[id] = nil; + return priority, item, id; + end +end +function indexed_heap:peek() + return self.priorities[1]; +end +function indexed_heap:reprioritize(id, priority) + local k = self.index[id]; + if k == nil then return; end + self.priorities[k] = priority; + + k = _percolate_up(self.priorities, k, self.ids, self.index); + k = _percolate_down(self.priorities, k, self.ids, self.index); +end +function indexed_heap:remove_index(k) + local size = #self.priorities; + + local result = self.priorities[k]; + local result_sync = self.ids[k]; + local item = self.items[result_sync]; + if result == nil then return; end + self.index[result_sync] = nil; + self.items[result_sync] = nil; + + self.priorities[k] = self.priorities[size]; + self.ids[k] = self.ids[size]; + self.index[self.ids[k]] = k; + t_remove(self.priorities); + t_remove(self.ids); + + k = _percolate_up(self.priorities, k, self.ids, self.index); + k = _percolate_down(self.priorities, k, self.ids, self.index); + + return result, item, result_sync; +end +function indexed_heap:remove(id) + return self:remove_index(self.index[id]); +end + +local mt = { __index = indexed_heap }; + +local _M = { + create = function() + return setmetatable({ + ids = {}; -- heap of ids, sync'd with priorities + items = {}; -- map id->items + priorities = {}; -- heap of priorities + index = {}; -- map of id->index of id in ids + current_id = 1.5 + }, mt); + end +}; +return _M; |