Create Hashset.lua

Author: sirwez

DataStructures/Hashset/Hashset.lua

@@ -0,0 +1,94 @@
+local hashset = {}
+
+hashset.__index = hashset
+
+hashset.Node = {}
+hashset.Node.__index = hashset.Node
+
+function hashset.Node.create(key)
+    local s = {}
+    setmetatable(s, hashset.Node)
+
+    s.key = key
+    s.next = nil
+
+    return s
+end
+
+function hashset.create(hash)
+    local s = {}
+    setmetatable(s, hashset)
+
+    if hash == nil then
+        hash = function(x) return x end
+    end
+
+    s.s = {}
+    s.N = 0
+    s.hash = hash
+
+    return s
+end
+
+function hashset:add(key)
+    local h = self.hash(key)
+    local x = self.s[h]
+    local found = false
+    while x ~= nil do
+        if x.key == key then
+            found = true
+            break
+        end
+        x = x.next
+    end
+
+    if found == false then
+        local old = self.s[h]
+        self.s[h] = hashset.Node.create(key)
+        self.s[h].next = old
+        self.N = self.N + 1
+    end
+
+end
+
+function hashset:contains(key)
+    local h = self.hash(key)
+    local x = self.s[h]
+    while x ~= nil do
+        if x.key == key then
+            return true
+        end
+        x = x.next
+    end
+    return false
+end
+
+function hashset:size()
+    return self.N
+end
+
+function hashset:isEmpty()
+    return self.N == 0
+end
+
+function hashset:remove(key)
+    local h = self.hash(key)
+    local x = self.s[h]
+    local prev_x = nil
+    while x ~= nil do
+        if x.key == key then
+            if prev_x == nil then
+                self.s[h] = x.next
+            else
+                prev_x.next = x.next
+            end
+            self.N = self.N - 1
+        end
+        prev_x = x
+        x = x.next
+    end
+
+    return nil
+end
+
+return hashset