Add strategy pattern example for solution

Author: leemhoon00

src/Strategy/Book/index.ts

@@ -0,0 +1,48 @@
+export interface RouteStrategy {
+  buildRoute(origin: string, destination: string): string;
+}
+
+class RoadStrategy implements RouteStrategy {
+  buildRoute(origin: string, destination: string): string {
+    return `Road route from ${origin} to ${destination}`;
+  }
+}
+
+class WalkingStrategy implements RouteStrategy {
+  buildRoute(origin: string, destination: string): string {
+    return `Walking route from ${origin} to ${destination}`;
+  }
+}
+
+class PublicTransportStrategy implements RouteStrategy {
+  buildRoute(origin: string, destination: string): string {
+    return `Public transport route from ${origin} to ${destination}`;
+  }
+}
+
+class Navigator {
+  private routeStrategy: RouteStrategy;
+
+  setRouteStrategy(strategy: RouteStrategy) {
+    this.routeStrategy = strategy;
+  }
+
+  buildRoute(origin: string, destination: string): string {
+    if (this.routeStrategy) {
+      return this.routeStrategy.buildRoute(origin, destination);
+    } else {
+      return "No route strategy set.";
+    }
+  }
+}
+
+const navigator = new Navigator();
+
+navigator.setRouteStrategy(new RoadStrategy());
+console.log(navigator.buildRoute("City A", "City B"));
+
+navigator.setRouteStrategy(new WalkingStrategy());
+console.log(navigator.buildRoute("Park X", "Museum Y"));
+
+navigator.setRouteStrategy(new PublicTransportStrategy());
+console.log(navigator.buildRoute("Station P", "Station Q"));