developed depth first search algorithm

Author: EvandroLG

algorithms/depth_first_search/depth_first_search.lua

@@ -0,0 +1,40 @@
+function _is_in_table(array, value)
+  for k, v in pairs(array) do
+    if v == value then return true end
+  end
+
+  return false
+end
+
+function _diff(first_table, second_table)
+  local output = {}
+
+  for k, v in pairs(first_table) do
+    if not _is_in_table(second_table, v) then
+      table.insert(output, v)
+    end
+  end
+
+  return output
+end
+
+function depth_first_search(graph, start)
+  local visited = {}
+  local stack = {start}
+  local vertex = nil
+
+  while #stack > 0 do
+    vertex = table.remove(stack)
+
+    if not _is_in_table(visited, vertex) then
+      table.insert(visited, vertex)
+      -- then add in the stack every node that's connect to
+      -- the current vertex, less the already visited nodes
+      stack = _diff(graph[vertex], visited)
+    end
+  end
+
+  return visited
+end
+
+return depth_first_search

algorithms/depth_first_search/test.lua

@@ -0,0 +1,21 @@
+package.path = './algorithms/?/?.lua;' .. package.path
+
+local dfs = require 'depth_first_search'
+local unittest = require 'unittest'
+local test = unittest.test
+local assert_equal = unittest.assert_equal
+
+test('return all the vertices of a given graph', function()
+  local graph = {
+    ['a'] = { 'b', 'c' },
+    ['b'] = { 'a', 'd', 'e' },
+    ['c'] = { 'a', 'f' },
+    ['d'] = { 'b' },
+    ['e'] = { 'b', 'f' },
+    ['f'] = { 'c', 'e' }
+  }
+
+  local vertices = dfs(graph, 'a')
+
+  assert_equal(#vertices, 6)
+end)