update Strategy pattern

Author: tk-codes

BehavioralPatterns/Strategy/README.md

@@ -4,27 +4,21 @@ The Strategy Pattern
 * defines a family of algorithms, 
 * encapsulates each one, and 
 * make them interchangeable. 
+
 Strategy lets the algorithm vary independently from clients that use it.
 
-![Duck App with Strategy Pattern](/Diagrams/Strategy.png)
+## Problem
 
-**Usage**
-```cs
-Duck mallard = new MallardDuck();
-mallard.PerformQuack();
-mallard.PerformFly();
+- A class should be configured with an algorithm instead of implementing an algorithm directly.
+- An algorithm should be selected and exchanged at run-time.
 
-// change the flying behavior dynamically
-Duck model = new ModelDuck();
-model.PerformFly(); // default behavior
-model.FlyBehavior = new FlyRocketPowered();  // set a different flying behavior at runtime
-model.PerformFly();
-```
+## Solution
 
+- Define an interface `Strategy` for performing an algorithm and define separate classes that implement the `Strategy` interface and encapsulate an algorithm in different ways.
 
 ## Common Structure
 
-![Common structure of strategy pattern](http://www.dofactory.com/images/diagrams/net/strategy.gif)
+![Common structure of strategy pattern](img/structure.jpg)
 
 * Strategy  (SortStrategy)
   * declares an interface common to all supported algorithms. Context uses this interface to call the algorithm defined by a ConcreteStrategy
@@ -35,4 +29,30 @@ model.PerformFly();
   * maintains a reference to a Strategy object
   * may define an interface that lets Strategy access its data.
 
-_[Source: http://www.dofactory.com/net/strategy-design-pattern]_
+## Collaboration
+
+- A context may pass all data required by the algorithm to the strategy when an algorithm is called.
+- A context forwards requests from its clients to its strategy. Clients usually create and pass a ConcreteStrategy object to the context; thereafter clients interact with the context exclusively.
+
+## Benefits
+
+## Drawbacks
+
+## Example
+
+![Duck App with Strategy Pattern](/Diagrams/Strategy.png)
+
+**Usage**
+```cs
+Duck mallard = new MallardDuck();
+mallard.PerformQuack();
+mallard.PerformFly();
+
+// change the flying behavior dynamically
+Duck model = new ModelDuck();
+model.PerformFly(); // default behavior
+model.FlyBehavior = new FlyRocketPowered();  // set a different flying behavior at runtime
+model.PerformFly();
+```
+
+## Relations with Other Patterns