Merge pull request #49 from dandynaufaldi/search-dfs

Add depth first search

Searches/depth_first_search.rb

@@ -0,0 +1,51 @@
+# @param [Integer] start
+# @param [Integer] target
+# @param [Array] adjacency_list
+# @return [Array] routes
+def dfs(start, target, adjacency_list)
+  is_visited = Hash.new(false)
+  parent = {}
+  stack = [start]
+  loop do
+    break if stack.empty?
+    current_node = stack.pop
+    is_visited[current_node] = true
+
+    return get_path(parent, target) if current_node == target
+
+    adjacency_list[current_node].each do |neighbor|
+      next if is_visited[neighbor]
+      stack << neighbor
+      is_visited[neighbor] = true
+      parent[neighbor] = current_node
+    end
+  end
+  []
+end
+
+# @param [Hash] parent
+# @param [Integer] dest
+# @return [Array] path
+def get_path(parent, dest)
+  iterator = dest
+  path = [dest]
+  while parent.has_key?(iterator)
+    path << parent[iterator]
+    iterator = parent[iterator]
+  end
+  path.reverse
+end
+
+def main
+  adjacency_list = [
+      [1, 2], #0
+      [0, 3], #1
+      [0, 3], #2
+      [1, 2, 4], #3
+      [3, 5], #4
+      [4] #5
+  ]
+  p dfs(0, 5, adjacency_list)
+end
+
+main