Just another update

Task/Priority-queue/C-sharp/priority-queue.cs

@@ -0,0 +1,60 @@
+using System;
+
+namespace PriorityQueue
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            PriorityQueue PQ = new PriorityQueue();
+            PQ.push(3, "Clear drains");
+            PQ.push(4, "Feed cat");
+            PQ.push(5, "Make tea");
+            PQ.push(1, "Solve RC tasks");
+            PQ.push(2, "Tax return");
+
+            while (!PQ.Empty)
+            {
+                var Val = PQ.pop();
+                Console.WriteLine(Val[0] + " : " + Val[1]);
+            }
+            Console.ReadKey();
+        }
+    }
+
+    class PriorityQueue
+    {
+        private System.Collections.SortedList PseudoQueue;
+
+        public bool Empty
+        {
+            get
+            {
+                return PseudoQueue.Count == 0;
+            }
+        }
+
+        public PriorityQueue()
+        {
+            PseudoQueue = new System.Collections.SortedList();
+        }
+
+        public void push(object Priority, object Value)
+        {
+            PseudoQueue.Add(Priority, Value);
+        }
+
+        public object[] pop()
+        {
+            object[] ReturnValue = { null, null };
+            if (PseudoQueue.Count > 0)
+            {
+                ReturnValue[0] = PseudoQueue.GetKey(0);
+                ReturnValue[1] = PseudoQueue.GetByIndex(0);
+
+                PseudoQueue.RemoveAt(0);
+            }
+            return ReturnValue;
+        }
+    }
+}

Task/Priority-queue/Clojure/priority-queue.clj

@@ -0,0 +1,19 @@
+user=> (use 'clojure.data.priority-map)
+
+; priority-map can be used as a priority queue
+user=> (def p (priority-map "Clear drains" 3, "Feed cat" 4, "Make tea" 5, "Solve RC tasks" 1))
+#'user/p
+user=> p
+{"Solve RC tasks" 1, "Clear drains" 3, "Feed cat" 4, "Make tea" 5}
+
+; You can use assoc or conj to add items
+user=> (assoc p "Tax return" 2)
+{"Solve RC tasks" 1, "Tax return" 2, "Clear drains" 3, "Feed cat" 4, "Make tea" 5}
+
+; peek to get first item, pop to give you back the priority-map with the first item removed
+user=> (peek p)
+["Solve RC tasks" 1]
+
+; Merge priority-maps together
+user=> (into p [["Wax Car" 4]["Paint Fence" 1]["Sand Floor" 3]])
+{"Solve RC tasks" 1, "Paint Fence" 1, "Clear drains" 3, "Sand Floor" 3, "Wax Car" 4, "Feed cat" 4, "Make tea" 5}

Task/Priority-queue/Lua/priority-queue-1.lua

@@ -0,0 +1,50 @@
+PriorityQueue = {
+    __index = {
+        put = function(self, p, v)
+            local q = self[p]
+            if not q then
+                q = {first = 1, last = 0}
+                self[p] = q
+            end
+            q.last = q.last + 1
+            q[q.last] = v
+        end,
+        pop = function(self)
+            for p, q in pairs(self) do
+                if q.first <= q.last then
+                    local v = q[q.first]
+                    q[q.first] = nil
+                    q.first = q.first + 1
+                    return p, v
+                else
+                    self[p] = nil
+                end
+            end
+        end
+    },
+    __call = function(cls)
+        return setmetatable({}, cls)
+    end
+}
+
+setmetatable(PriorityQueue, PriorityQueue)
+
+-- Usage:
+pq = PriorityQueue()
+
+tasks = {
+    {3, 'Clear drains'},
+    {4, 'Feed cat'},
+    {5, 'Make tea'},
+    {1, 'Solve RC tasks'},
+    {2, 'Tax return'}
+}
+
+for _, task in ipairs(tasks) do
+    print(string.format("Putting: %d - %s", unpack(task)))
+    pq:put(unpack(task))
+end
+
+for prio, task in pq.pop, pq do
+    print(string.format("Popped: %d - %s", prio, task))
+end

Task/Priority-queue/Lua/priority-queue-2.lua

@@ -0,0 +1,40 @@
+-- Use socket.gettime() for benchmark measurements
+-- since it has millisecond precision on most systems
+local socket = require("socket")
+
+n = 10000000 -- number of tasks added (10^7)
+m = 1000     -- number different priorities
+
+local pq = PriorityQueue()
+
+print(string.format("Adding %d tasks with random priority 1-%d ...", n, m))
+start = socket.gettime()
+
+for i = 1, n do
+    pq:put(math.random(m), i)
+end
+
+print(string.format("Elapsed: %.3f ms.", (socket.gettime() - start) * 1000))
+
+print("Retrieving all tasks in order...")
+start = socket.gettime()
+
+local pp = 0
+local pv = 0
+
+for i = 1, n do
+    local p, task = pq:pop()
+
+    -- check that tasks are popped in ascending priority
+    assert(p >= pp)
+
+    if pp == p then
+        -- check that tasks within one priority maintain the insertion order
+        assert(task > pt)
+    end
+
+    pp = p
+    pt = task
+end
+
+print(string.format("Elapsed: %.3f ms.", (socket.gettime() - start) * 1000))

Task/Priority-queue/Objective-C/priority-queue.m

@@ -14,12 +14,12 @@ CFComparisonResult PQCompare(const void *ptr1, const void *ptr2, void *unused) {
   int priority;
   NSString *name;
 }
-- (id)initWithPriority:(int)p andName:(NSString *)n;
+- (instancetype)initWithPriority:(int)p andName:(NSString *)n;
 - (NSComparisonResult)compare:(Task *)other;
 @end
 
 @implementation Task
-- (id)initWithPriority:(int)p andName:(NSString *)n {
+- (instancetype)initWithPriority:(int)p andName:(NSString *)n {
   if ((self = [super init])) {
     priority = p;
     name = [n copy];

Task/Priority-queue/Ruby/priority-queue.rb

@@ -1,7 +1,8 @@
 class PriorityQueueNaive
-  def initialize
-    @q = Hash.new { |h, k| h[k] = []}
-    @priorities = []
+  def initialize(data=nil)
+    @q = Hash.new {|h, k| h[k] = []}
+    data.each {|priority, item| @q[priority] << item}  if data
+    @priorities = @q.keys.sort
   end
 
   def push(priority, item)
@@ -20,7 +21,7 @@ class PriorityQueueNaive
   end
 
   def peek
-    if not empty?
+    unless empty?
       @q[@priorities[0]][0]
     end
   end
@@ -29,6 +30,25 @@ class PriorityQueueNaive
     @priorities.empty?
   end
 
+  def each
+    @q.each do |priority, items|
+      items.each {|item| yield priority, item}
+    end
+  end
+
+  def dup
+    @q.each_with_object(self.class.new) do |(priority, items), obj|
+      items.each {|item| obj.push(priority, item)}
+    end
+  end
+
+  def merge(other)
+    raise TypeError  unless self.class == other.class
+    pq = dup
+    other.each {|priority, item| pq.push(priority, item)}
+    pq                  # return a new object
+  end
+
   def inspect
     @q.inspect
   end
@@ -49,3 +69,14 @@ test.each {|pr, str| pq.push(pr, str) }
 until pq.empty?
   puts pq.pop
 end
+
+puts
+test2 = test.shift(3)
+p pq1 = PriorityQueueNaive.new(test)
+p pq2 = PriorityQueueNaive.new(test2)
+p pq3 = pq1.merge(pq2)
+puts "peek : #{pq3.peek}"
+until pq3.empty?
+  puts pq3.pop
+end
+puts "peek : #{pq3.peek}"