docs: add getting started

README.md

@@ -10,14 +10,101 @@ Package mcts provides parallel monte-carlo tree search for your Go applications.
 
 ## Installation
 
-Go latest is recommended
+Go latest is recommended.
 
 ```bash
 go get -u github.com/go-mcts/mcts
 ```
 
 ## Getting started
 
+See [examples](examples) directory.
+
+Implements `mcts.Move` and `mcts.State`:
+
+```go
+// examples/nim/nim.go
+type Move int
+
+type State struct {
+	playerToMove int
+	chips        int
+}
+
+func (s *State) PlayerToMove() int {
+	return s.playerToMove
+}
+
+func (s *State) HasMoves() bool {
+	s.checkInvariant()
+	return s.chips > 0
+}
+
+func (s *State) GetMoves() []mcts.Move {
+	s.checkInvariant()
+
+	var moves []mcts.Move
+	for i := 1; i <= min(3, s.chips); i++ {
+		moves = append(moves, i)
+	}
+	return moves
+}
+
+func (s *State) DoMove(move mcts.Move) {
+	m := move.(int)
+	if m < 1 || m > 3 {
+		panic("illegal move")
+	}
+	s.checkInvariant()
+
+	s.chips -= m
+	s.playerToMove = 3 - s.playerToMove
+
+	s.checkInvariant()
+}
+
+func (s *State) DoRandomMove(rd *rand.Rand) {
+	if s.chips <= 0 {
+		panic("invalid chips")
+	}
+	s.checkInvariant()
+
+	max := min(3, s.chips)
+	s.DoMove(rd.Intn(max) + 1)
+
+	s.checkInvariant()
+}
+
+func (s *State) GetResult(currentPlayerToMove int) float64 {
+	if s.chips != 0 {
+		panic("game not over")
+	}
+	s.checkInvariant()
+
+	if s.playerToMove == currentPlayerToMove {
+		return 1.0
+	}
+	return 0.0
+}
+
+func (s *State) Clone() mcts.State {
+	return &State{
+		playerToMove: s.playerToMove,
+		chips:        s.chips,
+	}
+}
+```
+
+Run `mcts.ComputeMove`:
+
+```go
+state := &State{
+	playerToMove: 1,
+	chips:        chips,
+}
+move := mcts.ComputeMove(state, mcts.MaxIterations(100000), mcts.Verbose(true))
+```
+
 ## License
 
 This project is under the MIT License. See the [LICENSE](LICENSE) file for the full license text.