lua-algorithms

This library was developed with the purpose of making general algorithms and data structures available in Java language also available in Lua.

Features

The library covers commonly used data structures (ArrayList, Stack, Queue, Priority Queue, Balanced Search Tree, HashMap, Set, Tries) and algorithms (various sorting and search algorithms, shuffling, union find, etc)

For developers on Windows platform, a Vagrantfile is provided in the source code to allow them to run luarocks under window environment.

Install

luarocks install lualgorithms

Usage

Common Data Structures

Stack

local stack = require 'lualgorithms.data.stack'

local s = stack.create()
s:push(1)
s:push(2)
s:push(3)
print(s:size())
print(s:isEmpty())
print(s:pop())
for index,val in pairs(s:enumerate()) do
    print(index, val)
end

ArrayList

The list behaves the same as the Java ArrayList API, and is zero-based indexing.

local list = require 'lualgorithms.data.list'

local s = list.create()
s:add(1) -- s becomes [1]
s:add(2) -- s becomes [1, 2]
s:add(3) -- s becomes [1, 2, 3]
s:set(2, 4) -- s becomes [1, 2, 4]

for index,val in pairs(s:enumerate()) do
    print(index, val)
end
for i = 0,s:size()-1 do
    print(s:get(i))
end
print(s:size())
print(s:isEmpty())
s:removeAt(0) -- s becomes [2, 4]
s:remove(2) -- s becomes [4]
s:removeAt(0) -- s is now empty

Queue

 local queue = require('lualgorithms.data.queue')
local s = queue.create()
s:enqueue(10)
s:enqueue(20)
s:enqueue(30)
print(s:size()) -- return 3
print(s:isEmpty()) -- return false
for key,value in pairs(s:enumerate()) do
    print(key, value)
end
print(s:dequeue()) -- return 10
print(s:dequeue()) -- return 20
print(s:dequeue()) -- return 30

MinPQ

local minpq = require('lualgorithms.data.minpq')
local comparer = function(a1, a2) return a1 - a2 end -- method that return negative value if if a1 < a2; 0 if a1 == a2; positive otherwise
local s = minpq.create(comparer)
s:enqueue(10)
s:enqueue(100)
s:enqueue(20)
s:enqueue(50)
print(s:size()) -- return 4
print(s:isEmpty()) -- return false

print(s:delMin()) -- return 10
print(s:delMin()) -- return 20
print(s:delMin()) -- return 50
print(s:delMin()) -- return 100

print(s:isEmpty()) -- return true

MaxPQ

local maxpq = require('lualgorithms.data.maxpq')
local comparer = function(a1, a2) return a1 - a2 end -- method that return negative value if if a1 < a2; 0 if a1 == a2; positive otherwise
local s = maxpq.create(comparer)
s:enqueue(10)
s:enqueue(100)
s:enqueue(20)
s:enqueue(50)
print(s:size()) -- return 4
print(s:isEmpty()) -- return false

print(s:delMax()) -- return 100
print(s:delMax()) -- return 50
print(s:delMax()) -- return 20
print(s:delMax()) -- return 10

print(s:isEmpty()) -- return true

HashSet

local hashset = require('lualgorithms.data.hashset')
local hash_func = function(x) return x % 1000 end
local s = hashset.create(hash_func)
s:add(100, 2)
s:add(200, 4)
s:add(450, 2)

print(s:contains(99)) -- return false
print(s:contains(100)) -- return true
print(s:size()) -- return 3
print(s:isEmpty()) -- return false
s:remove(100)
print(s:contains(100)) -- return false)

HashMap

local hashmap = require('lualgorithms.data.hashmap')
local hash_func = function(x) return x % 1000 end
local s = hashmap.create(hash_func)
s:put(100, 2)
s:put(200, 4)
s:put(450, 2)
print(s:get(100)) -- return  2
print(s:get(200)) -- return  4
print(s:get(450)) -- return  2
print(s:get(99)) -- return  nil
print(s:containsKey(99)) -- return  false
print(s:containsKey(100)) -- return  true
print(s:size()) -- return  3
print(s:isEmpty()) -- return  false
print(s:remove(100)) -- return  2
print(s:containsKey(100)) -- return  false
print(s:size()) -- return  2
s:remove(200)
s:remove(450)
print(s:isEmpty()) -- return  true

SortedMap (Left-Leaning Red Black Tree)

local map = require('lualgorithms.data.redblacktree')
local comparator = function(a1, a2) return a1 - a2 end
local s = map.create(comparator)
s:put(100, 2)
s:put(200, 4)
s:put(450, 2)
print(s:minKey()) -- return 100
print(s:maxKey()) -- return 450
print(s:get(100)) -- return  2
print(s:get(200)) -- return  4
print(s:get(450)) -- return  2
print(s:get(99)) -- return  nil
print(s:containsKey(99)) -- return  false
print(s:containsKey(100)) -- return  true
print(s:size()) -- return  3
print(s:isEmpty()) -- return  false
print(s:remove(100)) -- return  2
print(s:containsKey(100)) -- return  false
print(s:size()) -- return  2
s:remove(200)
s:remove(450)
print(s:isEmpty()) -- return  true

Tries (R-way Tries)

local rwaytries = require('lualgorithms.tries.rwaytries')
local s = rwaytries.create()

s:put("Hello", "World")
s:put("Hi", "Morning")
s:put("How", "are you?")

print(s:isEmpty()) -- return false
print(s:size()) -- return 3

print(s:get("Hello")) -- return "World"
print(s:get("Hi")) -- return "Morning"
print(s:get("How")) -- return "are you?"
print(s:containsKey("Hello")) -- return true
print(s:containsKey("hello")) -- return false

s:remove("Hello")

print(s:containsKey("Hello")) -- return false
print(s:size()) -- return 2

local keys = s:keys()
for i=0, keys:size()-1 do
    print(keys:get(i))
end

s:put('there', 'is')
s:put('the', 'ninja')
s:put('those', 'turtles')
s:put('these', 'ducks')
s:put('turles', 'ducks')
keys = s:keysWithPrefix('th')
for i=0, keys:size()-1 do
    print(keys:get(i))
end

Sorting

As in Java, the sorting is performed on ArrayList by default (which is lualgorithms.data.list).

Note that the default is to sort ascendingly, which can be reversed via the comparator function pass in as the second parameter.

Sorting (Selection Sort)

local list = require("lualgorithms.data.list")
local a = list.create()
a:add(100)
a:add(200)
a:add(300)
a:add(600)
a:add(200)
a:add(400)
a:add(340)
a:add(120)
a:add(10)

local selection = require("lualgorithms.sorting.selection")
selection.sort(a, function(a1, a2) return a1 - a2 end)

for i=0,(a:size()-1) do
    print(a:get(i))
end

Sorting (Insertion Sort)

local list = require("lualgorithms.data.list")
local a = list.create()
a:add(100)
a:add(200)
a:add(300)
a:add(600)
a:add(200)
a:add(400)
a:add(340)
a:add(120)
a:add(10)

local insertion = require("lualgorithms.sorting.insertion")
insertion.sort(a, function(a1, a2) return a1 - a2 end)

for i=0,(a:size()-1) do
    print(a:get(i))
end

Sorting (Shell Sort)

local list = require("lualgorithms.data.list")
local a = list.create()
a:add(100)
a:add(200)
a:add(300)
a:add(600)
a:add(200)
a:add(400)
a:add(340)
a:add(120)
a:add(10)

local shellsort = require("lualgorithms.sorting.shellsort")
shellsort.sort(a, function(a1, a2) return a1 - a2 end)

for i=0,(a:size()-1) do
    print(a:get(i))
end

Sorting (Merge Sort)

local list = require("lualgorithms.data.list")
local a = list.create()
a:add(100)
a:add(200)
a:add(300)
a:add(600)
a:add(200)
a:add(400)
a:add(340)
a:add(120)
a:add(10)

local mergesort = require("lualgorithms.sorting.mergesort")
mergesort.sort(a, function(a1, a2) return a1 - a2 end)

for i=0,(a:size()-1) do
    print(a:get(i))
end

Sorting (Quick Sort)

local list = require("lualgorithms.data.list")
local a = list.create()
a:add(100)
a:add(200)
a:add(300)
a:add(600)
a:add(200)
a:add(400)
a:add(340)
a:add(120)
a:add(10)

local quicksort = require("lualgorithms.sorting.quicksort")
quicksort.sort(a, function(a1, a2) return a1 - a2 end)

for i=0,(a:size()-1) do
    print(a:get(i))
end

Sorting (3-ways Quick Sort)

local list = require("lualgorithms.data.list")
local a = list.create()
a:add(100)
a:add(200)
a:add(300)
a:add(600)
a:add(200)
a:add(400)
a:add(340)
a:add(120)
a:add(10)

local quicksort3ways = require("lualgorithms.sorting.quicksort3ways")
quicksort3ways.sort(a, function(a1, a2) return a1 - a2 end)

for i=0,(a:size()-1) do
    print(a:get(i))
end

Sorting (Heap Sort)

local list = require("lualgorithms.data.list")
local a = list.create()
a:add(100)
a:add(200)
a:add(300)
a:add(600)
a:add(200)
a:add(400)
a:add(340)
a:add(120)
a:add(10)

local heapsort = require("lualgorithms.sorting.heapsort")
heapsort.sort(a, function(a1, a2) return a1 - a2 end)

for i=0,(a:size()-1) do
    print(a:get(i))
end

Shuffling

local list = require('lualgorithms.data.list')
local s = list.create()
for i=1,10 do
    s:add(i)
end
local shuffling = require('lualgorithms.shuffling')
shuffling.shuffle(s)
for i=0,(s:size()-1) do
    print(s:get(i))
end

Binary Search on Sorted ArrayList

local comparator = function(a1, a2) return a1 - a2 end
local s = create_a_list_that_sorts_ascendingly(comparator)

if s.isSortedAscedningly() then
    local binarysearch = require('lualgorithms.binarysearch')
    print(binarysearch.indexOf(s, 10, comparator)) -- return the index of value 10 in the array list s
else
    print('error! list must be sorted before performing binary search')    
end

Union Find

local unionfind = require('lualgorithms.unionfind').create()
unionfind:union(1, 2)
unionfind:union(4, 6)
unionfind:union(7, 4)

print(unionfind:connected(6, 7)) -- return true
print(unionfind:connected(4, 7)) -- return true
print(unionfind:connected(6, 4)) -- return true
print(unionfind:connected(6, 1)) -- return false
print(unionfind:connected(7, 2)) -- return false

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