【算法】公司食堂-美团2021校招笔试

https://www.nowcoder.com/questionTerminal/601815bea5544f389bcd20fb5ebca6a8

1.题目

2.我的解法（没有AC，运行超时）

代码

package 公司食堂;


import java.io.*;

/*
根据排队人的性别，从左到右判断是否优先做这个餐桌
遍历一轮没有优先桌，再遍历一遍选择次优
 */
public class CompanyCanteen {


    public static void companyCanteen(int[] peopleDispose, int M, char[] sexInQueue, int[] willGo) {
        int empty = 0;//空桌
        int onePeople = 0;//一人桌
        for (int i = 0; i < M; i++) {
            empty = 0;
            onePeople = 0;
            //标记空桌和一人桌
            //涉及第几桌要+1（因为从1开始）
            for (int j = 0; j < peopleDispose.length; j++) {
                if (onePeople == 0 && peopleDispose[j] == 1)
                    onePeople = j + 1;

                if (empty == 0 && peopleDispose[j] == 0)
                    empty = j + 1;

                if (onePeople != 0 && empty != 0)
                    break;
            }
            //判断男性和女性的结果,更新当前餐桌的人数
            /*
            男性没有1人桌了，才去空桌
            女性没有空桌了，才去一人桌
             */
            if (sexInQueue[i] == 'M') {
                if (onePeople == 0) {
                    willGo[i] = empty;
                    peopleDispose[empty - 1]++;
                } else {
                    willGo[i] = onePeople;
                    peopleDispose[onePeople - 1]++;
                }
            } else {
                if (empty == 0) {
                    willGo[i] = onePeople;
                    peopleDispose[onePeople - 1]++;
                } else {
                    willGo[i] = empty;
                    peopleDispose[empty - 1]++;
                }
            }
        }
    }

    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(System.out));


        int T = Integer.parseInt(reader.readLine());//数据组数
        int N;//餐桌个数
        int[] peopleDispose;//人数在餐桌上的排布
        int M;//排队人数
        char[] sexInQueue;//在排队的人的性别
        int[] willGo;//预测结果

        //每组数据占4行
        for (int i = 0; i < T; i++) {
            N = Integer.parseInt(reader.readLine());

            peopleDispose = new int[N];
            String disposeStr = reader.readLine();
            for (int j = 0; j < disposeStr.length(); j++) {
                //字符转数字时注意Ascll码
                peopleDispose[j] = disposeStr.charAt(j) - '0';
            }

            M = Integer.parseInt(reader.readLine());

            sexInQueue = new char[M];
            String sexInQueueStr = reader.readLine();
            for (int j = 0; j < sexInQueueStr.length(); j++) {
                sexInQueue[j] = sexInQueueStr.charAt(j);
            }

            willGo = new int[M];

            companyCanteen(peopleDispose, M, sexInQueue, willGo);
            for (int k = 0; k < willGo.length; k++) {
                writer.write(Integer.toString(willGo[k]));//输出必须是String类型的
                writer.newLine();
            }

            writer.flush();
        }
    }
}

不好在哪里

时间复杂度太高，把System输入输出改用BufferedReader和BufferedWriter也超时。每次循环都要找最左边的空桌和一人桌，大可不必，可以利用数据结构使其简便。

2.推荐解法：优先队列

代码

package 公司食堂;

import java.io.*;
import java.util.ArrayList;
import java.util.List;
import java.util.PriorityQueue;

/**
 * @author musecho801
 * @title CompanyCanteen1
 * @description 遍历桌号，将所有空桌、一人桌分别入队两个优先队列，
 * 根据性别判断会去哪个桌号
 * @date 2021/3/11 17:21
 */
public class CompanyCanteen1 {

    public void companyCanteen(String peopleDisposeStr, int M, String sexStr, int[] rs) {
        List<PriorityQueue> list = new ArrayList<>(2);
        PriorityQueue<Integer> emptyPQ = new PriorityQueue<>();
        PriorityQueue<Integer> oneTablePQ = new PriorityQueue<>();
        list.add(emptyPQ);
        list.add(oneTablePQ);
        int k = 0;//控制rs的下标

        //得到空桌、一人桌 两个优先队列(默认升序)
        //i为 桌号-1
        for (int i = 0; i < peopleDisposeStr.length(); i++) {
            if (peopleDisposeStr.charAt(i) == '0') {
                emptyPQ.add(i);
            } else if (peopleDisposeStr.charAt(i) == '1') {
                oneTablePQ.add(i);
            }
        }

        //根据性别判断会去哪个桌号
        for (int i = 0; i < sexStr.length(); i++) {
            //男性：只有没有一人桌时，才选择空桌
            if (sexStr.charAt(i) == 'M') {
                if (oneTablePQ.peek() != null) {
                    rs[k++] = oneTablePQ.poll();
                } else {
                    oneTablePQ.add(emptyPQ.peek());
                    rs[k++] = emptyPQ.poll();
                }
            } else if (sexStr.charAt(i) == 'F') {//女性：只有没有空桌时，才选择一人桌
                if (emptyPQ.peek() != null) {
                    oneTablePQ.add(emptyPQ.peek());
                    rs[k++] = emptyPQ.poll();
                } else {
                    rs[k++] = oneTablePQ.poll();
                }
            }
        }

        //注意：rs为去第i桌，值要+1
        for (int i = 0; i < M; i++)
            rs[i]++;
    }

    public static void main(String[] args) throws IOException {
        CompanyCanteen1 cc = new CompanyCanteen1();
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(System.out));

        int T = Integer.parseInt(reader.readLine());//数据组数
        for (int i = 0; i < T; i++) {
            int N = Integer.parseInt(reader.readLine());//餐桌个数
            String peopleDisposeStr = reader.readLine();//餐桌人数分布
            int M = Integer.parseInt(reader.readLine());//排队人数
            String sexStr = reader.readLine();//排队人的性别
            int[] rs = new int[M];//结果

            cc.companyCanteen(peopleDisposeStr, M, sexStr, rs);
            for (int t : rs) {
                writer.write(Integer.toString(t));
                writer.newLine();
            }
            //flush()冲刷出流，将所有缓冲数据强制发送至目的地。不加这个，是无法输出的
            writer.flush();
        }

    }
}

亮点

使用优先队列直接存储所有空桌、一人桌
BufferedReader和BufferedWriter的运行速度较快，学会使用

参考

posted @ 2021-03-12 11:39 musecho 阅读(462) 评论(0) 编辑收藏举报

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【算法】公司食堂-美团2021校招笔试

【算法】公司食堂-美团2021校招笔试

1.题目

2.我的解法（没有AC，运行超时）

2.推荐解法：优先队列

参考

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