50 lines
1.1 KiB
Lua
50 lines
1.1 KiB
Lua
local metatable = {__index = getfenv(1)}
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function less_than(a, b) return a < b end
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--> empty min heap
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function new(less_than)
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return setmetatable({less_than = less_than}, metatable)
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end
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function push(self, value)
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table.insert(self, value)
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local function heapify(index)
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if index == 1 then
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return
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end
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local parent = math.floor(index / 2)
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if self.less_than(self[index], self[parent]) then
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self[parent], self[index] = self[index], self[parent]
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heapify(parent)
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end
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end
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heapify(#self)
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end
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function pop(self)
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local value = self[1]
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local last = #self
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if last == 1 then
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self[1] = nil
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return value
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end
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self[1], self[last] = self[last], nil
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last = last - 1
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local function heapify(index)
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local left_child = index * 2
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if left_child > last then
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return
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end
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local smallest_child = left_child + 1
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if smallest_child > last or self.less_than(self[left_child], self[smallest_child]) then
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smallest_child = left_child
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end
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if self.less_than(self[smallest_child], self[index]) then
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self[index], self[smallest_child] = self[smallest_child], self[index]
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heapify(smallest_child)
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end
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end
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heapify(1)
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return value
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end |