Data commit

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))