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前言

博主偶然的一次刷题，发现了这个非常不错的网站牛客网，进去里面刷了一下，发现覆盖面非常的广，不仅有大厂的面试真题，还有小白的入门算法题，对刚刚接触计算机语言的人来说非常的友好，所以博主决定开启一个专栏，详细记录在牛客网的刷题思路讲解，大家一起跟随博主走入算法的大门吧！
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Java题目练习

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⭕题目一： 统计一句话中重复单词的个数

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🌟代码演示

import java.util.*;public class Main {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);String line = scanner.nextLine();Map<Character, Integer> map = new LinkedHashMap<Character, Integer>();for (int i = 0; i < line.length(); i++) {char c = line.charAt(i);if (c >= 'a' && c <= 'z' || c >= 'A' && c <= 'Z') {if (map.containsKey(c)) {map.put(c, map.get(c) + 1);} else {map.put(c, 1);}}}Set<Map.Entry<Character, Integer>> entrys = map.entrySet();for (Map.Entry<Character, Integer> entry : entrys) {System.out.println(entry.getKey() + ":" + entry.getValue());}}
}

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💯思路解析

       本题目思路是："使用一个map集合来解，因为map可以存储键值对，字母为键，次数为值即可，不过需要用的LinkedHashMap，因为这个是可以按照顺序输出的"

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⭕题目二： map简单应用

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🌟代码演示

import java.util.*;
public class Main {public static void main(String[] args) {Scanner scanner  = new Scanner(System.in);String name = scanner.next();Map<Integer, String> map = new HashMap<Integer, String>();map.put(1, "Amy");map.put(2, "Joe");map.put(3, "Tom");map.put(4, "Susan");//write your code here......Set<Map.Entry<Integer, String>> entries = map.entrySet();for (Map.Entry<Integer, String> entry : entries) {Integer key = entry.getKey();String value = entry.getValue();System.out.println(key+":"+value);}System.out.println(" ");map.put(5,name);map.remove(4);map.put(3,"Tommy");for (Map.Entry<Integer, String> entry : entries) {Integer key = entry.getKey();String value = entry.getValue();System.out.println(key+":"+value);}}
}

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💯思路解析

       本题目思路是："按照题目来即可"

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⭕题目三： 集合排序

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🌟代码演示

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Scanner;
public class Main {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);Customer customer1 = new Customer("小明",scanner.nextInt());Customer customer2 = new Customer("小军",scanner.nextInt());Customer customer3 = new Customer("小红",scanner.nextInt());List<Customer> customers = new ArrayList<>();customers.add(customer1);customers.add(customer2);customers.add(customer3);//write your code here......Collections.sort(customers);    System.out.println(customers);}
}class Customer implements Comparable<Customer>{private String name;private int consumption;public Customer(String name, int consumption) {this.name = name;this.consumption = consumption;}@Overridepublic String toString() {return "Customer{" +"name='" + name + '\'' +", consumption=" + consumption +'}';}@Overridepublic int compareTo(Customer o) {return  o.consumption-consumption;    //降序} }

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💯思路解析

       本题目思路是："重写接口的方法，改它们的排序规则即可"

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⭕题目四： 判断各类型字符个数

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🌟代码演示

//解法1：根据ASCII码来解
import java.util.*;
public class Main {public static void main(String[] args){Scanner rd= new Scanner(System.in);String a=rd.nextLine();char [] b=a.toCharArray();         //把字符串变成字符数组int english=0;int number=0;int space=0;int other=0;for (int i = 0; i < b.length; i++) {if(b[i]>='a'&&b[i]<='z'){english++;}else if(b[i]>='0'&&b[i]<='9'){number++;}else if(b[i]==' '){space++;}else {other++;}}System.out.println("英文字母"+english+"数字"+number+"空格"+space+"其他"+other);}
}----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------//解法2：直接用Character自带的方法进行检测
import java.util.Scanner;
public class Main {public static void main(String[] args) {int numbers = 0;int words = 0;int space = 0;int other = 0;Scanner scanner = new Scanner(System.in);String str = scanner.nextLine();//write your code here......char[] chars = str.toCharArray();for (int i = 0; i < chars.length; i++) {char c = chars[i];if (Character.isLetter(c)) {words++;} else if (Character.isDigit(c)) {numbers++;} else if (Character.isWhitespace(c)) {space++;} else {other++;}}System.out.println("英文字母" + words + "数字" + numbers + "空格" + space + "其他" + other);}
}

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💯思路解析

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    本题目思路是：解法1："根据ASCII码表来进行if else的判断"解法2: "直接用Character自带的方法进行检测，Character.isLetter：判断字符是不是英文；Character.isDigit：判断字符是不是数字；Character.isWhitespace：判断字符是不是空格"

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⭕题目五： 编写个人所得税计算程序

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🌟代码演示

import java.util.*;
public class Main {public static void main(String[] args) {List<Employee> employees = new ArrayList<>();//write your code here......Employee e1 = new Employee("小明",2500);Employee e2 = new Employee("小军",8000);Employee e3 = new Employee("小红",100000);employees.add(e1) ;employees.add(e2) ;employees.add(e3) ;Iterator it = employees.iterator();while(it.hasNext()){Employee e4 = (Employee) it.next() ;double num = e4.getSalary() - 3500.00;double sax = 0.0 ;if(num < 0 ){}else if(num <= 1500){sax = num * 0.03 - 0 ;}else if(num <= 4500){sax = num * 0.1 - 105 ;}else if(num <= 9000){sax = num * 0.2 - 555 ;}else if(num <= 35000){sax = num * 0.25 - 1005 ;}else if(num <= 55000){sax = num * 0.3 - 2755 ;}else if(num <= 80000){sax = num * 0.35 - 5505 ;}else if(num > 80000){sax = num * 0.45 - 13505 ;}System.out.println(e4.getName()+"应该缴纳的个人所得税是："+sax);}}
}
class Employee{private String name;private double salary;public Employee(String name, double salary) {this.name = name;this.salary = salary;}public String getName() {return name;}public double getSalary() {return salary;}
}

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💯思路解析

                 本题目思路:"根据题目来即可"

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⭕题目六：记录点赞用户

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🌟代码演示

import java.util.*;public class Main {public static void main(String[] args) {LikeRecorder recorder = new LikeRecorderImpl();Scanner scanner = new Scanner(System.in);while (scanner.hasNext()) {String name = scanner.next();recorder.like(name);}System.out.println(Arrays.toString(recorder.getLikeUsers()));}}/*** 点赞记录器*/
interface LikeRecorder {/*** 若用户没有点赞过，则记录此次点赞行为。* 若用户曾经点赞过，则删除用户点赞记录。** @param username 用户名*/void like(String username);/*** 返回所有点赞的用户名** @return 用户名数组*/String[] getLikeUsers();}class LikeRecorderImpl implements LikeRecorder {// write your code here......public HashSet<String> hs = new HashSet();public void like(String username){if(hs.contains(username)){hs.remove(username);}else{hs.add(username);}}public String[] getLikeUsers(){return hs.toArray(new String[hs.size()]);}}

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💯思路解析

                 本题目思路:"根据题目来即可"

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⭕题目七：回文数判断

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🌟代码演示

import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner console = new Scanner(System.in);Main main = new Main();int number = console.nextInt();System.out.println(main.palindromeNumber(number));}public Boolean palindromeNumber(int number) {String numStr = String.valueOf(number);char numChar[] = numStr.toCharArray();if (numChar[0]==numChar[4]&&numChar[1]==numChar[3]) {return true;}return false;
}}

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💯思路解析

                 本题目思路:"根据题目来即可"

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⭕题目八：判断素数个数

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🌟代码演示

import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);int start = scanner.nextInt();int end = scanner.nextInt();method(start,end);}public static boolean is_prime(int num){for(int i=2;i<num;i++){if(num%i==0)return false;}return true;}public static void method(int start, int end) {int count=0;//write your code here......if(end<start)start=start+end-(end=start);for(int i=start;i<=end;i++){if(i<=2)continue;if(is_prime(i))count++;}System.out.println(start+"到"+end+"之间有"+count+"个大于2的素数");}
}

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💯思路解析

                 本题目思路:"素数又叫质数，指的是在大于1的自然数中，除了1和它本身，没有别的因数，也就是如果一个数只能被1和它本身整除，那么这个数就叫做素数"

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⭕题目九： 根据周长求面积

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🌟代码演示

import java.util.Scanner;public class Main {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);while (scanner.hasNextDouble()) {double s = scanner.nextDouble();// Circle和Square是需要你定义的类System.out.println(String.format("%.3f",new Circle(s).getArea()));System.out.println(String.format("%.3f", new Square(s).getArea()));}}}class Shape {private double s; // 周长public Shape(double s) {this.s = s;}public double getS() {return s;}}interface Area {double getArea(); // 面积
}// 圆形
class Circle extends Shape implements Area {//write your code here......//调用父类的构造方法public Circle(double s){super(s);}//2πr = 圆的周长double r = super.getS() / (2 * Math.PI);public double getArea(){return Math.PI * r * r;}}// 方形
class Square extends Shape implements Area {//write your code here......public Square(double s){super(s);}//4a = 正方形周长double side = super.getS() / 4;public double getArea(){return side * side;}}

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💯思路解析

                     本题目思路是：根据题目描述来即可

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⭕题目十： 冒泡排序

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🌟代码演示

import java.util.Arrays;
import java.util.Scanner;
public class Main {public static void main(String[] args) {Scanner scanner = new Scanner(System.in);int[] arr = new int[7];for (int i = 0; i < arr.length; i++) {arr[i] = scanner.nextInt();}scanner.close();//write your code here......Arrays.sort(arr);for (int k = 0; k < arr.length; k++) {System.out.print(arr[k]+" ");}}
}

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💯思路解析

       本题目思路是："这里使用的是直接sort进行排序"

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✍ 结语

多刷刷题目，才能早日迈入大厂，巩固我们学习到的知识，下一期见，订阅专栏刷题不迷路
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作者：KJ.JK

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