Initial commit

gamemodes/darkrp/gamemode/libraries/disjointset.lua

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+/*---------------------------------------------------------------------------
+Disjoint-set forest implementation
+Inspired by the book Introduction To Algorithms (third edition)
+
+by FPtje Atheos
+
+Running time per operation (Union/FindSet): O(a(n)) where a is the inverse of the Ackermann function.
+---------------------------------------------------------------------------*/
+
+local ipairs = ipairs
+local setmetatable = setmetatable
+local string = string
+local table = table
+local tostring = tostring
+
+module("disjoint")
+
+local metatable
+
+-- Make a singleton set. Parent parameter is optional, must be a disjoint-set as well.
+function MakeSet(x, parent)
+    local set  = {}
+    set.value  = x
+    set.rank   = 0
+    set.parent = parent or set
+
+    setmetatable(set, metatable)
+
+    return set
+end
+
+local function Link(x, y)
+    if x == y then return x end
+
+    -- Union by rank
+    if x.rank > y.rank then
+        y.parent = x
+        return x
+    end
+
+    x.parent = y
+
+    if x.rank == y.rank then
+        y.rank = y.rank + 1
+    end
+
+    return y
+end
+
+-- Apply the union operation between two sets.
+function Union(x, y)
+    return Link(FindSet(x), FindSet(y))
+end
+
+function FindSet(x)
+    local parent = x
+    local listParents
+
+    -- Go up the tree to find the parent
+    while parent ~= parent.parent do
+        parent = parent.parent
+
+        listParents = listParents or {}
+        table.insert(listParents, parent)
+    end
+
+    -- Path compression, update all parents to refer to the top parent
+    if listParents then
+        for _, v in ipairs(listParents) do
+            v.parent = parent
+        end
+    end
+
+    return parent
+end
+
+function Disconnect(x)
+    x.parent = x
+
+    return x
+end
+
+
+metatable = {
+    __tostring = function(self)
+        return string.format("Disjoint-Set [value: %s][Rank: %s][Parent: %s]", tostring(self.value), self.rank, tostring(self.parent.value))
+    end,
+    __metatable = true, -- restrict access to metatable
+    __add = Union
+}