Major refactoring - migrate source vetex from Graph's constructor to …

…the iterate method as a param.

learning-lua/algo/BFS-tests.lua

@@ -12,8 +12,8 @@ end
 
 local function bfs_test(input, src, expected_visits, expected_max_level)
   local G = load_input(input)
-  local bfs, count, prev_level = BFS:new(G, src), 1, 0
-  for from, to, weight, level in bfs:iterate() do
+  local bfs, count, prev_level = BFS:new(G), 1, 0
+  for from, to, weight, level in bfs:iterate(src) do
     count = count + 1
     assert(prev_level <= level)
     prev_level = level

learning-lua/algo/BFS.lua

@@ -6,13 +6,13 @@ local E = {}
 
 local TO<const>, LEVEL<const> = 2, 4
 
-local function _iterate(self)
+local function _iterate(self, src)
   local q, visited = Queue:new(), {
-    [self.src_vertex] = true
+    [src] = true
   }
   self._visited_count = 1
   local level = 0
-  local from = self.src_vertex
+  local from = src
   repeat
     local vertex = self.graph:vertex(from)
     level = level + 1
@@ -31,9 +31,8 @@ local function _iterate(self)
 end
 
 ---@param G (table) graph
----@param src (any) source vertex
-function BFS:new(G, src, func_iterate)
-  return getmetatable(self):new(G, src, _iterate)
+function BFS:new(G, func_iterate)
+  return getmetatable(self):new(G, _iterate)
 end
 
 return BFS

learning-lua/algo/DFS-tests.lua

@@ -14,8 +14,8 @@ end
 
 local function dfs_test(input, src, expected_visits, expected_max_level)
   local G = load_edges(input)
-  local dfs, count, max_level = DFS:new(G, src), 1, 0
-  for from, to, weight, level in dfs:iterate() do
+  local dfs, count, max_level = DFS:new(G), 1, 0
+  for from, to, weight, level in dfs:iterate(src) do
     count = count + 1
     max_level = level > max_level and level or max_level
     -- print(string.format("%d: %s-%s=%d", level, from, to, weight))
@@ -31,9 +31,9 @@ local function topo_sort(input, src)
   local terminal -- the terminal node
   local level_visits = {}
   local G = load_edges(input)
-  local dfs = DFS:new(G, src)
+  local dfs = DFS:new(G)
   -- outgoings is the number of unvisited outgoing edges
-  for from, to, _, depth, outgoings in dfs:iterate() do
+  for from, to, _, depth, outgoings in dfs:iterate(src) do
     -- print(string.format("%d: %s-%s", level, from, to))
     if not terminal and outgoings == 0 then
       terminal = to
@@ -107,9 +107,9 @@ local function single_vertex_test()
   print("Testing single vertex ...")
   local G = Graph:new()
   G:add('a')
-  local dfs = DFS:new(G, 'a')
+  local dfs = DFS:new(G)
   local count = 0
-  for from, to, weight, depth in dfs:iterate() do
+  for from, to, weight, depth in dfs:iterate('a') do
     count = count + 1
     assert(from == 'a')
     assert(not to)

learning-lua/algo/DFS.lua

@@ -4,8 +4,8 @@ local Stack = require "algo.Stack"
 local DFS = GraphSearch:class()
 local E = {}
 
--- Element index of a stack entry with the format: {from, to, weight, depth, count_unvisited, begin_vertex}
-local FROM<const>, TO<const>, WEIGHT<const>, DEPTH<const>, UNVISITED<const>, BEGIN_VERTEX<const> = 1, 2, 3, 4, 5, 6
+-- Element index of a stack entry with the format: {from, to, weight, depth, count_unvisited, begin_vertex, is_visited}
+local FROM<const>, TO<const>, WEIGHT<const>, DEPTH<const>, UNVISITED<const>, BEGIN_VERTEX<const>, IS_VISITED<const> = 1, 2, 3, 4, 5, 6, 7
 
 local function debug(...)
   -- print(...)
@@ -60,15 +60,17 @@ local function vertices_of(G)
   return vertices
 end
 
-local function _iterate(self)
+---@param src (any) optional source vertex; this takes precedence.
+---@param is_include_visited (boolean) true if visited nodes are returned in addition to unvisited node.
+local function _iterate(self, src, is_include_visited)
   local stack, visited = Stack:new(), {}
   -- Applicable only if a single source is not specified for this DFS.
   -- If a single source is specified, the DFS will only be performed from that source vertex.
   -- Otherwise, DFS is performed from potentially many source vertices until all vertices have been explored.
   local unvisited_vertices -- Contains vertices that have not been visited; visited ones are erased.
   local src_spec_idx = 0
   self._visited_count = 0
-  local node = self.src_vertex -- DFS from a single source vertex
+  local node = src -- DFS from a single source vertex
   if not node then -- DFS from potentially many source vertices
     unvisited_vertices = vertices_of(self.graph)
     local next_unvisited = next(unvisited_vertices) -- we are done if all vertices have been visited.
@@ -132,11 +134,10 @@ local function _iterate(self)
 end
 
 ---@param G (table) graph
----@param src (any) source vertex
 ---@param nav_spec (table) opional navigation spec in the format of {from_1={to_1, to_2, ...}, ...} e.g. {['3']={'5','11'}, ['5']={'7','9'}}
 ---@param src_spec (table) optional source vertex spec in the format of {v1, v2, ...} e.g. {'1', '2', '3', ...}; applicable only if 'src' is not specified
-function DFS:new(G, src, nav_spec, src_spec)
-  return getmetatable(self):new(G, src, _iterate, nav_spec, src_spec)
+function DFS:new(G, nav_spec, src_spec)
+  return getmetatable(self):new(G, _iterate, nav_spec, src_spec)
 end
 
 return DFS

learning-lua/algo/GraphSearch.lua

@@ -13,11 +13,13 @@ local function _yield(entry)
 end
 
 ---@param src (any) optional source vertex; this takes precedence.
-function GraphSearch:iterate(src)
+---@param is_include_visited (boolean) true if visited nodes are returned in addition to unvisited node.  (Currently only DFS supports this parameter.)
+function GraphSearch:iterate(src, is_include_visited)
+  assert(not src or self.graph:vertex(src), "Source vertex not found in graph")
   self._visited_count = 0
   -- self._nav = build_navigation(self)
   return coroutine.wrap(function()
-    self:_iterate(src)
+    self:_iterate(src, is_include_visited)
   end)
 end
 
@@ -34,18 +36,14 @@ function GraphSearch:class(o)
 end
 
 ---@param G (table) graph
----@param src (any) source vertex (optional)
 ---@param func_iterate (function) function for iteration
 ---@param nav_spec (table) optional navigation spec in the format of {from_1={to_1, to_2, ...}, ...} e.g. {['3']={'5','11'}, ['5']={'7','9'}}
 ---@param src_spec (table) optional source vertex spec in the format of {v1, v2, ...} e.g. {'1', '2', '3', ...}; applicable only if 'src' is not specified
-function GraphSearch:new(G, src, func_iterate, nav_spec, src_spec)
+function GraphSearch:new(G, func_iterate, nav_spec, src_spec)
   assert(G, "Missing Graph")
   assert(Graph.isGraph(G), "G must be a graph object")
-  -- assert(src, "Missing source vertex")
-  assert(not src or G:vertex(src), "Source vertex not found in graph")
   local o = GraphSearch:class{
-    graph = G,
-    src_vertex = src
+    graph = G
   }
   o._iterate = func_iterate
   o._nav_spec = nav_spec or E

learning-lua/algo/SCCSearch.lua

@@ -52,7 +52,7 @@ end
 
 ---@param G (table) graph
 function SCCSearch:new(G)
-  return getmetatable(self):new(G, nil, _iterate)
+  return getmetatable(self):new(G, _iterate)
 end
 
 return SCCSearch

learning-lua/algo/SccDfsSearch.lua

@@ -38,7 +38,7 @@ local function _iterate(self)
   local scc_id, count = 0, 0
   local src_spec = reversed(src_spec)
   debug(table.concat(src_spec, ","))
-  local dfs = DFS:new(G, nil, nil, src_spec)
+  local dfs = DFS:new(G, nil, src_spec)
   local scc_src_vertex
   for from, to, _, _, _, src_vertex in dfs:iterate() do
     debug(string.format("from=%s to=%s, src_vertex=%s", from, to, src_vertex))
@@ -60,7 +60,7 @@ end
 
 ---@param G (table) graph
 function SccDfsSearch:new(G)
-  return getmetatable(SccDfsSearch):new(G, nil, _iterate)
+  return getmetatable(SccDfsSearch):new(G, _iterate)
 end
 
 return SccDfsSearch

learning-lua/algo/ShortestPathSearch-tests.lua

@@ -14,8 +14,8 @@ local function basic_tests()
   G:add('v', 't', 6)
   G:add('w', 't', 3)
 
-  local search = ShortestPathSearch:new(G, 's')
-  for from, to, weight, level, min_cost in search:iterate() do
+  local search = ShortestPathSearch:new(G)
+  for from, to, weight, level, min_cost in search:iterate('s') do
     debug(string.format("%d: %s-%s=%d, min:%d", level, from, to, weight, min_cost))
   end
 
@@ -43,8 +43,8 @@ local function tim_test()
   local src<const> = 's'
   local G = load_input(input)
   local level_counts = {}
-  local search = ShortestPathSearch:new(G, src)
-  for from, to, weight, level, min_cost in search:iterate() do
+  local search = ShortestPathSearch:new(G)
+  for from, to, weight, level, min_cost in search:iterate(src) do
     level_counts[level] = level_counts[level] or 0
     level_counts[level] = level_counts[level] + 1
     -- print(string.format("%d: %s-%s=%d, min:%d", level, from, to, weight, min_cost))
@@ -73,8 +73,8 @@ local function geek_test()
   local src<const> = '0'
   local G = load_input(input)
   local level_counts = {}
-  local search = ShortestPathSearch:new(G, src)
-  for from, to, weight, level, min_cost in search:iterate() do
+  local search = ShortestPathSearch:new(G)
+  for from, to, weight, level, min_cost in search:iterate(src) do
     level_counts[level] = level_counts[level] or 0
     level_counts[level] = level_counts[level] + 1
     -- print(string.format("%d: %s-%s=%d, min:%d", level, from, to, weight, min_cost))
@@ -122,8 +122,8 @@ local function redblobgames_test()
 
   local G = load_input(input)
   local level_counts = {}
-  local search = ShortestPathSearch:new(G, src)
-  for from, to, weight, level, min_cost in search:iterate() do
+  local search = ShortestPathSearch:new(G)
+  for from, to, weight, level, min_cost in search:iterate(src) do
     level_counts[level] = level_counts[level] or 0
     level_counts[level] = level_counts[level] + 1
     -- print(string.format("%d: %s-%s=%d, min:%d", level, from, to, weight, min_cost))
@@ -159,8 +159,8 @@ local function algodaily_test()
 
   local G = load_input(input)
   local level_counts = {}
-  local search = ShortestPathSearch:new(G, src)
-  for from, to, weight, level, min_cost in search:iterate() do
+  local search = ShortestPathSearch:new(G)
+  for from, to, weight, level, min_cost in search:iterate(src) do
     level_counts[level] = level_counts[level] or 0
     level_counts[level] = level_counts[level] + 1
     -- print(string.format("%d: %s-%s=%d, min:%d", level, from, to, weight, min_cost))
@@ -199,8 +199,8 @@ local function scott_moura_test()
 
   local G = load_input(input)
   local level_counts = {}
-  local search = ShortestPathSearch:new(G, src)
-  for from, to, weight, level, min_cost in search:iterate() do
+  local search = ShortestPathSearch:new(G)
+  for from, to, weight, level, min_cost in search:iterate(src) do
     level_counts[level] = level_counts[level] or 0
     level_counts[level] = level_counts[level] + 1
     -- print(string.format("%d: %s-%s=%d, min:%d", level, from, to, weight, min_cost))
@@ -241,8 +241,8 @@ local function negative_tests()
   print("ShortestPathSearch negative_tests...")
   local G = Graph:new()
   G:add('s', 'v', -1)
-  local search = ShortestPathSearch:new(G, 's')
-  local iterator = search:iterate()
+  local search = ShortestPathSearch:new(G)
+  local iterator = search:iterate('s')
   local ok, errmsg = pcall(iterator, search)
   assert(not ok)
   assert(string.match(errmsg, "Weight must not be negative$"))

learning-lua/algo/ShortestPathSearch.lua

@@ -6,38 +6,6 @@ local E = {}
 
 local FROM<const>, TO<const>, WEIGHT<const>, DEPTH<const>, COST_SO_FAR<const> = 1, 2, 3, 4, 5
 
--- Uses Dijkstra's algorithm
-local function _iterate(self)
-  local G, s, sssp = self.graph, self.src_vertex, self.sssp
-  local heap = BinaryHeap:new({}, function(a, b)
-    local a, b = a[TO], b[TO]
-    return sssp.vertices[a].min_cost <= sssp.vertices[b].min_cost
-  end)
-  local depth = 0
-  local node = self.src_vertex
-  repeat
-    sssp.vertices[node].ref = nil -- nullify from's heap reference as from is no longer on the heap
-    local vertex = self.graph:vertex(node)
-    depth = depth + 1
-    for to, weight in vertex:outgoings() do
-      assert(weight >= 0, "Weight must not be negative")
-      local v_info, v_cost_so_far = sssp.vertices[to], sssp.vertices[node].min_cost + weight
-      if v_cost_so_far < v_info.min_cost then
-        v_info.min_cost = v_cost_so_far
-        v_info.from = node
-        local v_ref = v_info.ref
-        if v_ref then
-          local entry = heap:remove(v_ref.pos)
-          assert(entry[TO] == to, string.format("removed: %s, to: %s", entry[TO], to)) -- remove from heap if necessary before adding
-        end
-        v_info.ref = heap:add{node, to, weight, depth, v_cost_so_far}
-      end
-    end
-    local item = self._yield(heap:remove())
-    node, depth = item[TO], item[DEPTH]
-  until not node -- note a cyclical path would lead to infinite iteration
-end
-
 local function shortest_path_of(sssp, dst)
   local path = {assert(dst)}
   local from = sssp.vertices[dst].from
@@ -80,6 +48,39 @@ local function new_sssp(s)
   return sssp
 end
 
+-- Uses Dijkstra's algorithm
+local function _iterate(self, src)
+  self.sssp = new_sssp(src)
+  local G, sssp = self.graph, self.sssp
+  local heap = BinaryHeap:new({}, function(a, b)
+    local a, b = a[TO], b[TO]
+    return sssp.vertices[a].min_cost <= sssp.vertices[b].min_cost
+  end)
+  local depth = 0
+  local node = src
+  repeat
+    sssp.vertices[node].ref = nil -- nullify from's heap reference as from is no longer on the heap
+    local vertex = self.graph:vertex(node)
+    depth = depth + 1
+    for to, weight in vertex:outgoings() do
+      assert(weight >= 0, "Weight must not be negative")
+      local v_info, v_cost_so_far = sssp.vertices[to], sssp.vertices[node].min_cost + weight
+      if v_cost_so_far < v_info.min_cost then
+        v_info.min_cost = v_cost_so_far
+        v_info.from = node
+        local v_ref = v_info.ref
+        if v_ref then
+          local entry = heap:remove(v_ref.pos)
+          assert(entry[TO] == to, string.format("removed: %s, to: %s", entry[TO], to)) -- remove from heap if necessary before adding
+        end
+        v_info.ref = heap:add{node, to, weight, depth, v_cost_so_far}
+      end
+    end
+    local item = self._yield(heap:remove())
+    node, depth = item[TO], item[DEPTH]
+  until not node -- note a cyclical path would lead to infinite iteration
+end
+
 --- ShortestPathSearch.lua enables graph traveral using an iterator
 --- (while following the Dijkstra’s graph search strategy).
 --- Notes:
@@ -93,9 +94,8 @@ end
 --- * No full computation on the entire graph necessary a priori.
 ---@param G (table) graph
 ---@param src (any) source vertex
-function ShortestPathSearch:new(G, src)
-  local o = getmetatable(self):new(G, src, _iterate)
-  o.sssp = new_sssp(src)
+function ShortestPathSearch:new(G)
+  local o = getmetatable(self):new(G, _iterate)
   o.shortest_paths = function(self)
     return self.sssp
   end

learning-lua/algo/TopologicalSearch.lua

@@ -17,7 +17,7 @@ local function _iterate(self, src)
   if src then
     stack:push(src)
   end
-  for from, to in DFS:new(self.graph, src, nav_spec, src_spec):iterate() do
+  for from, to in DFS:new(self.graph, nav_spec, src_spec):iterate(src) do
     if not src then -- This condition can be true at most once at the beginning of a topo search.
       debug(string.format("Topo search starting from %s", from))
       src = from
@@ -55,7 +55,7 @@ end
 ---@param nav_spec (table) optional navigation spec in the format of {from_1={to_1, to_2, ...}, ...} e.g. {['3']={'5','11'}, ['5']={'7','9'}}
 ---@param src_spec (table) optional source vertex spec in the format of {v1, v2, ...} e.g. {'1', '2', '3', ...}; applicable only if a single source vertex is not specified
 function TopologicalSearch:new(G, nav_spec, src_spec)
-  return getmetatable(self):new(G, nil, _iterate, nav_spec, src_spec)
+  return getmetatable(self):new(G, _iterate, nav_spec, src_spec)
 end
 
 return TopologicalSearch