From e5840321e27be6674052e7b665f8f26e789df9c0 Mon Sep 17 00:00:00 2001
From: Karma Riuk <riukkarma@gmail.com>
Date: Thu, 10 Aug 2023 19:39:16 +0200
Subject: [PATCH] Added a solver: turn left

---
 solver/turn_left.go | 63 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)
 create mode 100644 solver/turn_left.go

diff --git a/solver/turn_left.go b/solver/turn_left.go
new file mode 100644
index 0000000..b9f9677
--- /dev/null
+++ b/solver/turn_left.go
@@ -0,0 +1,63 @@
+package solver
+
+import (
+	"maze-solver/maze"
+	"maze-solver/utils"
+)
+
+type TurnLeftSolver struct {
+	visited map[*maze.Node]bool
+}
+
+func (s *TurnLeftSolver) Solve(m *maze.Maze) *maze.SolvedMaze {
+	defer utils.Timer("Turn left algorithm", 2)()
+
+	current, end := m.Nodes[0], m.Nodes[len(m.Nodes)-1]
+	s.visited = make(map[*maze.Node]bool, len(m.Nodes))
+
+	for _, node := range m.Nodes {
+		s.visited[node] = false
+	}
+
+	stack := make([]*maze.Node, 0, len(m.Nodes))
+	stack = append(stack, current)
+
+	for current != end {
+		s.visited[current] = true
+
+		left_visited, right_visited, up_visited, down_visited := s.wasVisited(current.Left), s.wasVisited(current.Right), s.wasVisited(current.Up), s.wasVisited(current.Down)
+
+		if left_visited && right_visited && up_visited && down_visited {
+			// dead end or no more visited nodes
+			stack = stack[:len(stack)-1]
+			current = stack[len(stack)-1]
+		} else {
+
+			if !left_visited {
+				current = current.Left
+			} else if !down_visited {
+				current = current.Down
+			} else if !right_visited {
+				current = current.Right
+			} else if !up_visited {
+				current = current.Up
+			}
+
+			stack = append(stack, current)
+		}
+	}
+
+	ret := &maze.SolvedMaze{
+		Maze:     m,
+		Solution: stack,
+	}
+	return ret
+}
+
+func (s *TurnLeftSolver) wasVisited(node *maze.Node) bool {
+	if node == nil {
+		return true
+	}
+	visited, _ := s.visited[node]
+	return visited
+}