separate chaining hashmap implementation

Author: chen0040

src/data/hashedmap.lua

@@ -0,0 +1,117 @@
+--
+-- Created by IntelliJ IDEA.
+-- User: chen0
+-- Date: 26/6/2017
+-- Time: 12:48 AM
+-- To change this template use File | Settings | File Templates.
+--
+
+local hashmap = {}
+
+hashmap.__index = hashmap
+
+hashmap.Node = {}
+hashmap.Node.__index = hashmap.Node
+
+function hashmap.Node.create(key, value)
+    local s = {}
+    setmetatable(s, hashmap.Node)
+
+    s.key = key
+    s.value = value
+    s.next = nil
+
+    return s
+end
+
+function hashmap.create(hash)
+    local s = {}
+    setmetatable(s, hashmap)
+
+    if hash == nil then
+        hash = function(x) return x end
+    end
+
+    s.s = {}
+    s.N = 0
+
+    return s
+end
+
+function hashmap:put(key, value)
+    local h = self:hash(key)
+    local x = self.s[h]
+    local found = false
+    while x ~= nil do
+        if x.key == key then
+            found = true
+            x.value = value
+            break
+        end
+        x = x.next
+    end
+
+    if found == false then
+        local old = self.s[h]
+        self.s[h] = hashmap.Node.create(key,value)
+        self.s[h].next = old
+        self.N = self.N + 1
+    end
+
+end
+
+function hashmap:get(key)
+    local h = self:hash(key)
+    local x = self.s[h]
+    while x ~= nil do
+        if x.key == key then
+            return x.value
+        end
+        x = x.next
+    end
+    return nil
+end
+
+function hashmap:containsKey(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 hashmap:size()
+    return self.N
+end
+
+function hashmap:isEmpy()
+    return self.N == 0
+end
+
+function hashmap: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
+            local value = x.value
+            if prev_x == nil then
+                self.s[h] = x.next
+            else
+                prev_x.next = x.next
+            end
+            return value
+        end
+        prev_x = x
+        x = x.next
+    end
+
+    return nil
+end
+
+return hashmap
+

src/data/hashmap.lua

@@ -99,11 +99,7 @@ end
 function list.ArrayList:resize(newSize)
     local temp = {}
     for i = 0,(newSize-1) do
-        if self.a[i] == nil then
-            temp[i] = nil
-        else
-            temp[i] = self.a[i]
-        end
+        temp[i] = self.a[i]
     end
 
     self.a = temp

src/data/list.lua

@@ -100,11 +100,7 @@ end
 function stack.ArrayStack:resize(newSize)
     local temp = {}
     for i = 0,(newSize-1) do
-        if self.a[i] == nil then
-            temp[i] = nil
-        else
-            temp[i] = self.a[i]
-        end
+        temp[i] = self.a[i]
     end
 
     self.a = temp