昨儿看爱情公寓5,剧里面偷了道题目
啤酒2块钱一瓶,4个瓶盖或者2个空瓶能再换1瓶啤酒,问10块钱最多能喝多少瓶啤酒。
这道题明显是一道递归算法题,弹幕里很多人算出来是15瓶,但是赵海棠最后得出的答案是20瓶。
其实都是正确答案,15瓶是指所有的啤酒都是自己买的情况下,最后剩下3个瓶盖和一个空酒瓶,喝了15瓶啤酒。
而20瓶的答案是通过先预支20瓶啤酒得出的。预支20瓶啤酒喝掉后剩下的瓶盖和酒瓶可以兑换15瓶啤酒。这个时候你还没有付钱,10块钱正好可以再买5瓶啤酒,这5瓶啤酒加上兑换的15瓶正好可以还20瓶啤酒回去。也就是说只花了10元但是喝了20瓶酒,最后所有的酒瓶和瓶盖都兑换掉了。
这里要注意的是酒瓶,瓶盖加上啤酒才是完整的一瓶酒。
用java实现一下,这题用面向过程的编程思想方便一些
package com.bai.psychedelic.bear;
import java.util.ArrayList;
public class Beer {
private int mUnitPrice = 2;
private int mCapCount = 0;
private int mBottleCount = 0;
private int mTotalMoney = 100;
private int mBeerSize = 0;
private int mSurplusMoney = 0;
private int mBottleToBeer = 0;
private int mCapToBeer = 0;
/**
* 设置多少瓶盖能换一瓶啤酒
*/
public void setmCapToBeer(int mCapToBeer) {
this.mCapToBeer = mCapToBeer;
}
/**
* 设置多少空瓶能换一瓶啤酒
*/
public void setmBottleToBeer(int mBottleToBeer) {
this.mBottleToBeer = mBottleToBeer;
}
/**
* 设置啤酒单价
*/
public void setmUnitPrice(int mUnitPrice) {
this.mUnitPrice = mUnitPrice;
}
/**
* 设置总共有多少钱
* @param mTotalMoney
*/
public void setmTotalMoney(int mTotalMoney) {
this.mTotalMoney = mTotalMoney;
this.mSurplusMoney = mTotalMoney;
}
/**
* 每次计算前clean之前的数据
*/
public void clean() {
mUnitPrice = 0;
mCapCount = 0;
mBottleCount = 0;
mBeerSize = 0;
mSurplusMoney = 0;
mCountBeerSize = 0;
mBottleToBeer = 0;
mCapToBeer = 0;
}
/**
*
* @param list
*/
public void buyBeer(ArrayList<String> list) {
if (mSurplusMoney >= mUnitPrice) {
mSurplusMoney = mSurplusMoney - mUnitPrice;
addOneBeer();
}
if (mBottleCount >= mBottleToBeer) {
mBottleCount = mBottleCount - mBottleToBeer;
addOneBeer();
}
if (mCapCount >= mCapToBeer) {
mCapCount = mCapCount - mCapToBeer;
addOneBeer();
}
list.add("啤酒数量:" + mBeerSize + " 剩余:" + mSurplusMoney + "元 " +
"酒瓶数量:" + mBottleCount + " " +
"瓶盖数量:" + mCapCount);
if (mSurplusMoney < mUnitPrice && mBottleCount < 2 && mCapCount < 4) {
} else {
buyBeer(list);
}
}
private int mCountBeerSize = 0;
/**
* 计算指定数量的啤酒可以兑换多少啤酒,对count()的封装
* @param size
* @return
*/
public int countBeer(int size) {
count(size, size, size);
return mCountBeerSize - size;
}
/**
* 计算给定数量的酒瓶、瓶盖或者完整的啤酒可以兑换多少瓶啤酒
* @param capsize
* @param bottlesize
* @param beersize
*/
private void count(int capsize, int bottlesize, int beersize) {
if (capsize >= 4) {
beersize++;
capsize = capsize - 4;
}
if (bottlesize >= 2) {
beersize++;
bottlesize = bottlesize - 2;
}
if (!(capsize < 4 && bottlesize < 2)) {
count(capsize, bottlesize, beersize);
} else {
mCountBeerSize = beersize;
}
}
/**
* 兑换或者买一瓶完整的啤酒,同时获得酒瓶瓶盖
*/
private void addOneBeer() {
mBeerSize++;
mBottleCount++;
mCapCount++;
}
}
就不放在Main方法里测试了,干脆写一个Android计算器demo
MainActivity:
package com.bai.psychedelic.bear;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
private Button mBtnReturned,mBtnNoReturned;
private EditText mBeerPrice,mTotalMoney,mStrategyCap,mStrategyBottle,mBeerReturned;
private RecyclerView mRecyclerView;
private Beer mBeer;
private RvResultAdapter mAdapter;
private ArrayList<String> mList;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
initView();
mBeer = new Beer();
mList = new ArrayList<>();
mAdapter = new RvResultAdapter(mList);
mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
mRecyclerView.setAdapter(mAdapter);
}
private void initView() {
mBtnReturned = findViewById(R.id.main_bt_count_returned);
mBtnNoReturned = findViewById(R.id.main_bt_count_no_returned);
mBeerPrice = findViewById(R.id.main_ed_beer_price);
mTotalMoney = findViewById(R.id.main_ed_total_money);
mStrategyCap = findViewById(R.id.main_ed_beer_strategy_cap);
mStrategyBottle = findViewById(R.id.main_ed_beer_strategy_bottle);
mBeerReturned = findViewById(R.id.main_ed_beer_returned);
mRecyclerView = findViewById(R.id.main_rv_result);
}
public void noReturnedClick(View view) {
mBeer.clean();
int beerPrice = Integer.parseInt(mBeerPrice.getText().toString());
int totalMoney = Integer.parseInt(mTotalMoney.getText().toString());
mBeer.setmTotalMoney(totalMoney);
mBeer.setmUnitPrice(beerPrice);
mBeer.setmCapToBeer(Integer.parseInt(mStrategyCap.getText().toString()));
mBeer.setmBottleToBeer(Integer.parseInt(mStrategyBottle.getText().toString()));
mBeer.buyBeer(mList);
mAdapter.notifyDataSetChanged();
}
public void returnedClick(View view) {
mBeer.clean();
int count = Integer.parseInt(mBeerReturned.getText().toString());
int beerPrice = Integer.parseInt(mBeerPrice.getText().toString());
int totalMoney = Integer.parseInt(mTotalMoney.getText().toString());
mBeer.setmTotalMoney(totalMoney);
mBeer.setmUnitPrice(beerPrice);
mBeer.setmCapToBeer(Integer.parseInt(mStrategyCap.getText().toString()));
mBeer.setmBottleToBeer(Integer.parseInt(mStrategyBottle.getText().toString()));
int result = mBeer.countBeer(count);
mList.clear();
mList.add("预支"+count+"瓶啤酒可兑换"+result+"瓶啤酒,还需买"+(count-result)+"瓶啤酒还回去");
mList.add("买"+(count-result)+"瓶啤酒需要"+(Integer.parseInt(mBeerPrice.getText().toString()))*(count-result)+"元");
mAdapter.notifyDataSetChanged();
}
}
activity_main.xml:
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">
<EditText
android:id="@+id/main_ed_total_money"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:hint="输入买酒的钱"
android:inputType="number"
app:layout_constraintBottom_toTopOf="@+id/main_ed_beer_price"
app:layout_constraintLeft_toLeftOf="parent"/>
<EditText
android:id="@+id/main_ed_beer_price"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:hint="输入啤酒单价"
android:inputType="number"
app:layout_constraintTop_toBottomOf="@+id/main_ed_total_money"
app:layout_constraintLeft_toLeftOf="parent"
/>
<EditText
android:id="@+id/main_ed_beer_strategy_cap"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:hint="输入能兑换啤酒的瓶盖数量"
android:inputType="number"
app:layout_constraintLeft_toRightOf="@+id/main_ed_beer_price"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintRight_toRightOf="parent"/>
<EditText
android:id="@+id/main_ed_beer_strategy_bottle"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:hint="输入能兑换啤酒的空酒瓶数量"
android:inputType="number"
app:layout_constraintLeft_toRightOf="@+id/main_ed_beer_price"
app:layout_constraintTop_toBottomOf="@+id/main_ed_beer_strategy_cap"
app:layout_constraintRight_toRightOf="parent"
/>
<Button
android:id="@+id/main_bt_count_no_returned"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="不能退换情况下计算总共能喝多少啤酒"
app:layout_constraintTop_toBottomOf="@+id/main_ed_beer_strategy_bottle"
android:onClick="noReturnedClick"
/>
<EditText
android:id="@+id/main_ed_beer_returned"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:hint="输入需要预支多少瓶啤酒"
android:inputType="number"
app:layout_constraintTop_toBottomOf="@+id/main_bt_count_no_returned"
app:layout_constraintRight_toRightOf="parent"
/>
<Button
android:id="@+id/main_bt_count_returned"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="能退换情况下计算总共能喝多少啤酒"
app:layout_constraintTop_toBottomOf="@+id/main_ed_beer_returned"
android:onClick="returnedClick"
/>
<androidx.recyclerview.widget.RecyclerView
android:id="@+id/main_rv_result"
android:layout_width="match_parent"
android:layout_height="0dp"
app:layout_constraintTop_toBottomOf="@+id/main_bt_count_returned"
app:layout_constraintBottom_toBottomOf="parent"
/>
</androidx.constraintlayout.widget.ConstraintLayout>
ResultAdapter:
package com.bai.psychedelic.bear;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.TextView;
import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;
import java.util.ArrayList;
public class RvResultAdapter extends RecyclerView.Adapter<RvResultAdapter.ViewHolder> {
private ArrayList<String> mList;
public RvResultAdapter(ArrayList<String> mList) {
this.mList = mList;
}
static class ViewHolder extends RecyclerView.ViewHolder{
TextView mTextView;
public ViewHolder(@NonNull View itemView) {
super(itemView);
mTextView = itemView.findViewById(R.id.rv_item_tv);
}
}
@NonNull
@Override
public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.rv_result_item,parent,false);
ViewHolder viewHolder = new ViewHolder(view);
return viewHolder;
}
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
holder.mTextView.setText(mList.get(position));
}
@Override
public int getItemCount() {
return mList.size();
}
}
rv_result_item.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="@+id/rv_item_tv"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="结果"
android:gravity="center"
/>
</LinearLayout>
APP运行效果如下~
Video:
018f3fb77015e03ea82520829008e42c
其实我认为这题不用递归用生产者消费者模式也可以搞定,但是麻烦一些。马上8点了我要去看阿狗了,不写了,有兴趣自己试嗷!