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| /** | |
| * Definition for a binary tree node. | |
| * public class TreeNode { | |
| * int val; | |
| * TreeNode left; | |
| * TreeNode right; | |
| * TreeNode(int x) { val = x; } | |
| * } | |
| */ | |
| import java.lang.reflect.Constructor; | |
| import java.lang.reflect.InvocationTargetException; | |
| import java.lang.reflect.Parameter; | |
| import java.util.ArrayList; | |
| import java.util.HashMap; | |
| import java.util.List; | |
| import java.util.Map; | |
| public class Solution { | |
| public TreeNode invertTree(TreeNode root) { | |
| Injector injector = Injector.create(new InvertTreeModule()); | |
| InvertTreeSolver solver = injector.getInstance(InvertTreeSolver.class); | |
| return solver.solve(root); | |
| } | |
| public static class Injector { | |
| public static Injector create(Module module) { | |
| return new Injector(module); | |
| } | |
| private final Module module; | |
| public Injector(Module module) { | |
| this.module = module; | |
| module.configure(); | |
| } | |
| public <T> T getInstance(Class<T> type) { | |
| Constructor<?>[] constructors = type.getConstructors(); | |
| Constructor<?> firstConstructor = constructors[0]; | |
| Parameter[] params = firstConstructor.getParameters(); | |
| List<Object> args = new ArrayList<>(); | |
| for (Parameter param : params) { | |
| Class bindingType = module.getBinding(param.getType()); | |
| try { | |
| args.add(bindingType.newInstance()); | |
| } catch (InstantiationException | IllegalAccessException ex) { | |
| return null; | |
| } | |
| } | |
| try { | |
| return (T) firstConstructor.newInstance(args.toArray(new Object[args.size()])); | |
| } catch (InstantiationException | IllegalAccessException | IllegalArgumentException | InvocationTargetException ex) { | |
| return null; | |
| } | |
| } | |
| } | |
| public abstract static class Module { | |
| private final Map<Class, Class> classMap = new HashMap<>(); | |
| public abstract void configure(); | |
| protected <T> void bind(Class<T> from, Class<? extends T> to) { | |
| classMap.put(from, to); | |
| } | |
| public Class getBinding(Class from) { | |
| return classMap.get(from); | |
| } | |
| } | |
| public static class InvertTreeModule extends Module { | |
| @Override | |
| public void configure() { | |
| bind(InvertTreeStrategy.class, AwesomeInvertTreeStrategy.class); | |
| } | |
| } | |
| public static class InvertTreeSolver { | |
| private final InvertTreeStrategy strategy; | |
| public InvertTreeSolver(InvertTreeStrategy strategy) { | |
| this.strategy = strategy; | |
| } | |
| public TreeNode solve(TreeNode root) { | |
| return strategy.invertTree(root); | |
| } | |
| } | |
| public static interface InvertTreeStrategy { | |
| public TreeNode invertTree(TreeNode root); | |
| } | |
| public static class AwesomeInvertTreeStrategy implements InvertTreeStrategy { | |
| @Override | |
| public TreeNode invertTree(TreeNode root) { | |
| if (root == null) { | |
| return null; | |
| } | |
| TreeNode tmp = root.left; | |
| root.left = root.right; | |
| root.right = tmp; | |
| invertTree(root.left); | |
| invertTree(root.right); | |
| return root; | |
| } | |
| } | |
| } |
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