马蜂窝2020秋招java方向笔试

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本文链接： https://blog.csdn.net/Miaoshuowen/article/details/102502487

题目：
输入多个8位的id加城市的名字，23112411-beijing 这样，然后统计签到人数前三个城市，同一个ID城市多次签到同一个城市只记一次，次数相同时，则按城市首字母顺序排列。
示例：
输入：

34839946-beijing 
34839934-beijing 
34839946-beijing 
34839946-shanghai
34839912-hangzhou
-1

输出：

city=beijing, citycount=2
city=hangzhou, citycount=1
city=shanghai, citycount=1

思路：
输入时通过一个HashMap将重复签到的数据过滤，然后再利用一个HashMap统计所有城市的签到次数，最后将HashMap中的数据排序。排序有多种选择：
①冒泡排序，新建String的数组，存储城市名，通过索引HashMap中的value将数组排序
②通过Collections.sort排序
详细的Collections.sort用法链接：https://www.cnblogs.com/yw0219/p/7222108.html?utm_source=itdadao&utm_medium=referral

代码：Collections.sort排序

public class Mafengwo1 implements Comparable<Mafengwo1> {

	private String city;
	private int citycount;

	public String getCity() {
		return city;
	}

	public void setCity(String city) {
		this.city = city;
	}

	public int getCitycount() {
		return citycount;
	}

	public void setCitycount(int citycount) {
		this.citycount = citycount;
	}

	public Mafengwo1(String city, int citycount) {
		this.city = city;
		this.citycount = citycount;
	}

	public Mafengwo1() {
		
	}

	static Map<String, Integer> map = new HashMap<String, Integer>();

	static Map<String, Integer> map2 = new HashMap<String, Integer>();

	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		String str = new String();
		str = in.next();
		while (!str.equals("-1")) {

			map.put(str, 1);

			str = in.next();
		}

		in.close();
		Mafengwo1 test = new Mafengwo1();
		test.city(map);
	}

	
	public void city(Map<String, Integer> map) {

		for (String str : map.keySet()) {
			String str2 = new String();
			str2 = str.substring(9);
			map2.put(str2, map2.getOrDefault(str2, 0) + 1);

		}

		int i = 0;
		List<Mafengwo1> empList = new ArrayList<>();
		for (String k : map2.keySet()) {
			Mafengwo1 emp = new Mafengwo1(k, map2.get(k));
			empList.add(emp);
		}
		Collections.sort(empList, Comparator.reverseOrder());
		while(i<3) {
			System.out.println(empList.get(i));
			i++;
		}
		
	}

	@Override
	public String toString() {
		return " city=" + city + ", citycount=" + citycount;
	}

	
	@Override
	public int compareTo(Mafengwo1 o) {

		if (this.getCitycount() - o.getCitycount() == 0) {
			return o.getCity().compareTo(this.getCity());
		}
		return this.getCitycount() - o.getCitycount();
	}
}