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Trace: • Scala • Angular • Observer Pattern • Strategy Pattern
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design_pattern:strategy_pattern [2017/10/29 09:40] – ledyxdesign_pattern:strategy_pattern [2021/02/07 03:30] (current) – [Strategy Pattern] ledyx
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 **알고리즘(전략)을 전부 교체**해서 수정하기 쉽도록 만들기 **알고리즘(전략)을 전부 교체**해서 수정하기 쉽도록 만들기
  
-{{tag>Architecture Modeling DesignPattern Behavioral}}+  * 언제 쓰면 좋을까? 
 +    * 원래 알고리즘과 개선된 알고리즘의 속도 비교 
 +    * 장기 게임에서 사용자의 난이도 선택에 따른 루틴 교체 
 +  * 장점? 
 +    * 실행중에도 교체 가능! (예제 Client의 Player 초기화 부분 확인)
  
 +{{tag>Architecture Modeling Design_Pattern Behavioral}}
 +
 +시나리오 : 가위바위보 게임
 +
 += Strategy =
 +<sxh java ; collapse:true>
 +public class Hand {
 + public static final int HANDVALUE_ROCK = 0;
 + public static final int HANDVALUE_SCISSORS = 1;
 + public static final int HANDVALUE_PAPER = 2;
 +
 + private static final Hand[] hand = {
 + new Hand(HANDVALUE_ROCK),
 + new Hand(HANDVALUE_SCISSORS),
 + new Hand(HANDVALUE_PAPER)
 + };
 +
 + private static final String[] name = {
 + "주먹", "가위", "보"
 + };
 +
 + private int handValue;
 +
 + private Hand(int handValue) {
 + this.handValue = handValue;
 + }
 +
 + public static Hand getHand(int handValue) {
 + return hand[handValue];
 + }
 +
 + public boolean isStgrongerThan(Hand h) {
 + return fight(h) == 1;
 + }
 +
 + public boolean isWeakerThan(Hand h) {
 + return fight(h) == -1;
 + }
 +
 + private int fight(Hand h) {
 + if(this == h)
 + return 0;
 + else if((this.handValue + 1) % 3 == h.handValue)
 + return 1;
 + else
 + return -1;
 + }
 +
 + @Override
 + public String toString() {
 + return name[handValue];
 + }
 +}
 +</sxh>
 +
 +<sxh java ; title:Strategy>
 +public interface Strategy {
 + Hand nextHand();
 + void study(boolean win);
 +}
 +</sxh>
 +
 +<sxh java ; title:ConcreteStrategy>
 +/* 이긴손 다시 내기 */
 +public class WinningStrategy implements Strategy {
 +
 + private Random random;
 + private boolean won = false;
 + private Hand prevHand;
 +
 + public WinningStrategy() {
 + this.random = new Random();
 + }
 +
 + @Override
 + public Hand nextHand() {
 + if(!won)
 + prevHand = Hand.getHand(random.nextInt(3));
 +
 + return prevHand;
 + }
 +
 + @Override
 + public void study(boolean win) {
 + won = win;
 + }
 +}
 +</sxh>
 +
 +<sxh java ; title:ConcreteStrategy>
 +/* 과거 승패 이력으로 확률적으로 바꾸기 */
 +public class ProbStrategy implements Strategy {
 +
 + private Random random;
 + private int prevHandValue;
 + private int currentHandValue;
 + private int[][] history = {
 + {1, 1, 1},
 + {1, 1, 1},
 + {1, 1, 1}
 + };
 +
 + public ProbStrategy() {
 + this.random = new Random();
 + }
 +
 + @Override
 + public Hand nextHand() {
 + int bet = random.nextInt(getSum(currentHandValue));
 + int handValue = 0;
 + if(bet < history[currentHandValue][0])
 + handValue = 0;
 + else if(bet < history[currentHandValue][0] + history[currentHandValue][1])
 + handValue = 1;
 + else
 + handValue = 2;
 +
 + prevHandValue = currentHandValue;
 + currentHandValue = handValue;
 +
 + return Hand.getHand(handValue);
 + }
 +
 + private int getSum(int hv) {
 + return IntStream.range(0, 3).map(i -> history[hv][i]).sum();
 + }
 +
 + @Override
 + public void study(boolean win) {
 + if(win)
 + history[prevHandValue][currentHandValue]++;
 + else {
 + history[prevHandValue][(currentHandValue + 1) % 3]++;
 + history[prevHandValue][(currentHandValue + 2) % 3]++;
 + }
 + }
 +}
 +</sxh>
 +
 +
 += Context =
 +Strategy를 이용하는 역할.
 +
 +<sxh java ; title:Context ; highlight:[3]>
 +public class Player {
 + private String name;
 + private Strategy strategy; // 위임!
 +
 + private int winCount;
 + private int loseCount;
 + private int gameCount;
 +
 + public Player(String name, Strategy strategy) {
 + super();
 + this.name = name;
 + this.strategy = strategy;
 + }
 +
 + public Hand nextHand() {
 + return strategy.nextHand();
 + }
 +
 + public void win() {
 + strategy.study(true);
 + winCount++;
 + gameCount++;
 + }
 +
 + public void lose() {
 + strategy.study(true);
 + loseCount++;
 + gameCount++;
 + }
 +
 + public void even() {
 + gameCount++;
 + }
 +
 + @Override
 + public String toString() {
 + return "Player [name=" + name + ", winCount=" + winCount + ", loseCount=" + loseCount
 + + ", gameCount=" + gameCount + "]";
 + }
 +}
 +</sxh>
 +
 +
 += Client =
 +<sxh java>
 +public class Main {
 + public static void main(String[] args) {
 +
 + Player player1 = new Player("철수", new WinningStrategy());
 + Player player2 = new Player("영희", new ProbStrategy());
 +
 + IntStream.range(0, 10000).forEach(i -> {
 + Hand nextHand1 = player1.nextHand();
 + Hand nextHand2 = player2.nextHand();
 +
 + if(nextHand1.isStgrongerThan(nextHand2)) {
 + System.out.println("Winner : " + player1.toString());
 + player1.win();
 + player2.lose();
 + }
 + else if(nextHand2.isStgrongerThan(nextHand1)) {
 + System.out.println("Winner : " + player2.toString());
 + player1.lose();
 + player2.win();
 + }
 + else {
 + System.out.println("Even!");
 + player1.even();
 + player2.even();
 + }
 + });
 +
 + System.out.println("\nTotal result:");
 + System.out.println(player1.toString());
 + System.out.println(player2.toString());
 + }
 +}
 +
 +/*
 +...
 +Winner : Player [name=영희, winCount=7843, loseCount=2135, gameCount=9997]
 +Winner : Player [name=영희, winCount=7844, loseCount=2135, gameCount=9998]
 +Winner : Player [name=영희, winCount=7845, loseCount=2135, gameCount=9999]
 +
 +Total result:
 +Player [name=철수, winCount=2135, loseCount=7846, gameCount=10000]
 +Player [name=영희, winCount=7846, loseCount=2135, gameCount=10000]
 +*/
 +</sxh>
design_pattern/strategy_pattern.1509270054.txt.gz · Last modified: 2021/02/07 03:15 (external edit)