Warehouse.java

import java.util.*;
// 记得导入类

/**
 * @author Junhao Wang
 * @date 01/05/2020
 */

// 注意不要用下划线命名！


// Warehouse.java
public class Warehouse {

  // main
  public static void main(String[] args) {
    Warehouse wh = new Warehouse();
    // test1
    wh.addProduct(new Product("p1"));
    wh.addProduct(new Product("p1"));
    wh.addProduct(new Product("p2"));
    wh.addProduct(new Product("p3"));
    wh.addProduct(null);
    System.out.println(wh.productMap);
    // test2
    boolean result = wh.satisfyOrder(Arrays.asList("p1", "p2", "p1"));
    System.out.println(result); // true
    result = wh.satisfyOrder(Arrays.asList("p1", "p2", "p2"));
    System.out.println(result); // false
    // test3
    result = wh.removeProduct("p1");
    System.out.println(result); // true
    System.out.println(wh.productMap);
    // test4
    result = wh.returnOrder(Arrays.asList("p1", "p2"));
    System.out.println(result);
    System.out.println(wh.productMap);
  }


  private Map<String, List<Product>> productMap; // <productID, product list>
  private Queue<Product> productQueue;

  // Constructor
  public Warehouse() {
    productMap = new HashMap<>();
    productQueue = new LinkedList<>();
  }

  // 1. Returns true if the product has been successfully added
  public boolean addProduct(Product product) {
    // check
    if (product == null) {
      return false;
    }
    String pid = product.getProductID();
    List<Product> list = productMap.getOrDefault(pid, new ArrayList<>());
    list.add(product);
    productMap.put(pid, list);
    return true;
  }


  // 2. Returns true if the warehouse satisfies the order list
  public boolean satisfyOrder(List<String> productIDList) {
    // check
    if (productIDList == null || productIDList.size() == 0) {
      return true;
    }
    // count products in the list
    Map<String, Integer> countMap = new HashMap<>();
    for (String pid : productIDList) {
      int count = countMap.getOrDefault(pid, 0);
      countMap.put(pid, count + 1);
    }
    // compare (for each pid)
    for (String pid : countMap.keySet()) {
      int count = countMap.get(pid);
      List<Product> list = productMap.getOrDefault(pid, null);
      if (list == null || count < list.size()) { // careful
        return false;
      }
    }
    return true;
  }

  // 3. Returns true if the product has been deleted
  // 如果是 removeProduct(Product product)? (set?
  public boolean removeProduct(String productID) {
    // check
    if (productID == null) {
      return false;
    }
    if (!productMap.containsKey(productID)) {
      return false;
    }
    // remove
    List<Product> list = productMap.get(productID);
    list.remove(list.size() - 1);
    if (list.size() > 0) {
      productMap.put(productID, list);
    } else {
      productMap.remove(productID);
    }

    return true;
  }

  // 4. Returns true if an order has been successfully returned
  public boolean returnOrder(List<String> productIDList) {
    // check
    if (productIDList == null || productIDList.size() == 0) {
      return false;
    }
    for (String pid : productIDList) {
      boolean result = removeProduct(pid);
      if (result == false) {
        System.out.println("There is no more \"" + pid + "\" product.");
      }
    }
    return true;
  }



  private static class Product {
    private String productID;

    public Product(String pid) {
      productID = pid;
    }

    public String getProductID() {
      return productID;
    }
  }


}