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LintCode Java教程 练习题答案

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本文字数： 14k 阅读时长 ≈ 13 分钟

Java 基础语法：语法、变量与运算

2160 · 打印 “Hello Java”

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public class Solution {
    /* Your first java code
     * print Hello Java to console
     */
    public static void main(String[] args) {
        // write your code here
		System.out.print("Hello Java");
    }
}

2157 · 打印 Welcome to LintCode!

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public class Solution {
    public static void main(String[] args) {
        // write your code here
        System.out.print("Welcome to LintCode!");
    }
}

2289 · 字符的ASCII码（Java 版）

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import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        // write your code here
        Scanner scan = new Scanner(System.in);
        char c= scan.next().charAt(0);
        System.out.println(c+0);
    }
}

2814.ASCII码对应的字符（Java 版）

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import java.util.*;

public class Main {
	public static void main(String[] args){
		// write your code here
		Scanner sc = new Scanner(System.in);
		int num = sc.nextInt();
		if(num<128 && num >=0){
				System.out.println(num>0?(char)num:"error");	
		}else{
			System.out.println("error");
		}
		
        sc.close();
        
  }
}

2759 · Integer 的取值范围

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public class Solution {
    
    public boolean equivalence(Integer a, Integer b) {
        // write your code here
        return a.equals(b);
    }
}

2611 · 判断两个数组是否相等

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import java.util.*;

public class Solution {
    public boolean equalityOfArrays(int[] arr1, int arr2[]) {
        // -- write your code here --
        Arrays.sort(arr1);
        Arrays.sort(arr2);
        if(Arrays.equals(arr1,arr2))
            return true;
        else
            return false;
    }
}

2166 · 简单的加减乘除运算

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public class Solution {
    public int addition(int a, int b) {
        // write your code here
        return a + b;       
    }

    public int subtraction(int a, int b) {
        // write your code here
        return a - b;
    }

    public int multiplication(int a, int b) {
        // write your code here
        return a * b;
    }

    public float division(int a, int b) {
        // write your code here
        return (float)a / b;
    }
}

2826 · 数字 2 的朋友

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public class Solution {
    public static boolean isFriend(int n) {
        // write your code here
        return Integer.bitCount(n) == 2;
    }
}

2820 · 小数字的和

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import java.util.*;

public class Main {
	public static void main(String[] args){
        // write your code here
        Scanner scan=new Scanner(System.in);
        int len=scan.nextInt();
        int[] s=new int[len];
        for(int i=0; i<len; i++){
            s[i]=scan.nextInt();
        }
        //求最大
        int max=Arrays.stream(s).max().orElse(0);
        //过滤并求和
        int total=Arrays.stream(s).filter(f -> f!=max).sum();
        System.out.println(total);	
  }
}

2823 · 这是什么三角形？

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import java.util.*;

public class Main {
	public static void main(String[] args){
        // write your code here
        Scanner cin = new Scanner(System.in);

        int a = cin.nextInt();
        int b = cin.nextInt();
        int c = 180 - a -b;

        if (a > 0 && b > 0 && c > 0) {
          if (a + b == 90) {
            System.out.println("直角三角形");
          }
          else if (a + b < 90) { //c > 90
            System.out.println("钝角三角形");
          }
          else {
            System.out.println("锐角三角形");
          }
        } else {
          System.out.println("无法组成三角形");
        }
  }
}

2515 · 唯一存在的数字

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import java.util.*;

public class Solution {
    /**
     * @param nums: Represents the incoming number
     * @return: A int value representing whether the
     *          return is a palindrome or not
     */
    public int uniqueNumber(int nums[]) {
        // write your code here
        int ans = 0;
        for(int i = 0; i < nums.length; i++){
            ans ^= nums[i];
        }
        return ans;
    }
}

Java 控制语句：分支与循环

2411 · 打印每月含有的天数

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import java.util.Scanner;


class Main {
    public static void main(String[] args) {
        // write your code here
        // read data from console
        Scanner sc = new Scanner(System.in);
        int year = sc.nextInt();
        int month = sc.nextInt();

        // output the answer to the console according to the
        // requirements of the question
        switch (month) {
        case 1:
        case 3:
        case 5:
        case 7:
        case 8:
        case 10:
        case 12:
            System.out.println("31 days");

            break;

        case 4:
        case 6:
        case 9:
        case 11:
            System.out.println("30 days");

            break;

        case 2:

            if ((((year % 4) == 0) && ((year % 100) != 0)) ||
                    ((year % 400) == 0)) {
                System.out.println("29 days");
            } else {
                System.out.println("28 days");
            }

            break;
        }
    }
}

2323 · 命中率评级 （Java 版）

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import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        // write your code here
        // read data from console
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        // output the answer to the console according to the
        // requirements of the question
        switch(n/10){
            case 10:
            System.out.println("A");
            break;
            case 9:
            System.out.println("A");
            break;
            case 8:
            System.out.println("B");
            break;
            case 7:
            System.out.println("C");
            break;
            case 6:
            System.out.println("D");
            break;
            default:
            System.out.println("E");
        }
    }
}

2290 · 求最大公约数（Java 版）

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public class Main {
    public static void main(String[] args) {
        int a = Integer.parseInt(args[0]);
        int b = Integer.parseInt(args[1]);
        // write your code here
        // please print the greatest common divisor of a and b
        int res = 1;
        int minval = Math.min(a,b);
        int maxVal = Math.max(a,b);

        if(maxVal % minval == 0)
        {
            System.out.println(minval);
            return;
        }
        while (a % 2 == 0 && b % 2 == 0)
        {
            res *= 2;
            a /= 2;
            b /= 2;
        }
        while (a % 3 == 0 && b % 3== 0)
        {
            res *= 3;
            a /= 3;
            b /= 3;
        }
        while (a%5 ==0 && b%5==0)
        {
            res *= 5;
            a /= 5;
            b /= 5;
        }
        System.out.println(res);
    }
}

2813 · 求 1 — 100 的偶数和

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public class Main {
	public static void main(String[] args) {
		// write your code here
		int res = 0;
		int i = 0;
		while(i <= 100)
		{
			res += i;
			i += 2;
		}
		System.out.println("Even sum of 1 - 100: "+res);
	}
}

2259 · 求和（Java 版）

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import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        // write your code here
        // read data from console
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        // output the answer to the console according to the requirements of the question
        System.out.println((1+n)*n/2);
    }
}

2822 · 截取下标为5的字符

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import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		// write your code here
		Scanner sc=new Scanner(System.in);//创建Scanner对象
		String s=sc.next();               //创建输入一个字符串
		char[] ch=s.toCharArray();		  //将字符串转化为char型数组
		System.out.print(ch[5]);		  //输出char型数组下标为5的数据
	}
}

2825 · 判断字符串是否相等

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import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		// write your code here
		Scanner sc = new Scanner(System.in);
		String str1 = sc.nextLine();
		String str2 = sc.nextLine();

		System.out.println(str1.equals(str2));
	}
}

2336 · 字符串中的字母大小写转换

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public class Solution {
    /**
     * @param str:   Indicates the string passed in
     * @return:  means return the case-converted string
     */
    public String alphabetConversion(String str) {
        // write your code here
        String s = "";
        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);           
            if (c>='A'&&c<='Z') {
                c += 32;
                s += c;
            }else if(c>='a'&&c<='z'){
                c -= 32;
                s += c;
            }else if(c>='0'&&c<='9'){
                s += c;
            }
        }
        return s;
    }
}

2408 · 字符串字符排序

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import java.util.Arrays;
public class Solution {
    /**
     * @param str: Arbitrary non-empty string
     * @return String in alphabetical ascending order
     */
    public String handle(String str) {
        // write your code here
        char[] chars = str.toCharArray();
        Arrays.sort(chars);
        // 将数组转化成字符串
        return String.valueOf(chars);
    }
}

2828 · 拼接字符串并改为大写

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public class Main {
	public static void main(String[] args) {
        String str1 = "I love ";
		String str2 = "China";
		// write your code here
		str1 = str1.concat(str2);
		str1 = str1.toUpperCase();
		System.out.println(str1);
	}
}

2329 · 求直角坐标系内两点间距离（Java 版）

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import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        // write your code here
        // read data from console
        Scanner sc = new Scanner(System.in);
        int x1 = sc.nextInt();
        int y1 = sc.nextInt();
        int x2 = sc.nextInt();
        int y2 = sc.nextInt();
        // output the answer to the console according to the
        // requirements of the question
        double distance = Math.sqrt(((x1 - x2) * (x1 - x2)) +
                ((y1 - y2) * (y1 - y2)));
        System.out.printf("%.2f\n", distance);
    }
}

2283 · 圆型周长（Java 版）

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public class Main {
    public static void main(String[] args) {
        int r = Integer.parseInt(args[0]);
        // write your code here
        // please print the perimeter of the circle
        System.out.printf("%.2f",2*Math.PI*r);
    }
}

2289 · 字符的ASCII码（Java 版）

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import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        // write your code here
        Scanner scan = new Scanner(System.in);
        char c= scan.next().charAt(0);
        System.out.println(c+0);
    }
}

2837 · 复制指定元素

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public class Main {
	public static void main(String[] args) {
        int[] arr={1,2,3,4,5,6,7,8,9};
		// write your code here
		int [] newArr = new int[5];

		for(int i=0;i<5;i++){
			newArr[i] = arr[i];
			System.out.print(newArr[i]+" ");
		}
	}
}

2838 · 随机生成数字

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import java.util.Random;
import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		// write your code here
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		Random r = new Random(n);
		for(int i = 0;i<50;i++){
			System.out.println(r.nextInt(n)+1);
		}
	}
}

2675 · 日期格式转换

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import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.*;

public class Solution {

    public String dateConversion(String str) throws ParseException {
        // -- write your code here --
        Date date = new SimpleDateFormat("yyyy-MM-dd").parse(str);
        return new SimpleDateFormat("yyyy年M月d日").format(date);
    }
}

2829 · 简单的手机号码验证

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import java.util.regex.*;
public class Solution {
    public static boolean isMatch(String s) {
        // write your code here
        Pattern p = Pattern.compile("^1[3-9]{1}[0-9]{9}+$");
        Matcher m = p.matcher(s);
        return m.matches();
    }
}

2832 · 简单校验一下邮箱格式

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import java.util.regex.*;
public class Solution {
    public static boolean isMatch(String s) {
        // write your code here
        String regex = "^[^0-9]\\w*([.+-]\\w+)*@[a-z0-9]+(.com)+(\\.[\\.a-zA-Z0-9]+)*";
        Pattern pattern = Pattern.compile(regex);
        Matcher matcher = pattern.matcher(s); 
        return matcher.matches();
    }
}

2840 · 简单的字符串匹配替换

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import java.util.regex.*;
public class Solution {
    public static String replaceString (String str, String replacement) {
        // write your code here
        return str.replaceAll("[\\]/\\|~!@#$%\\^&\\*\\(\\);:_\\+\\-\\[\\]]+", replacement);
    }
}

Java 面向对象入门

2848 · 完善合适的类

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class Solution{
	//write your code here
	protected int age;
	protected String name;
	
	protected void show() {
		String str = "Name: " + this.name + ", age: " + String.valueOf(this.age);
		System.out.println(str);
	}
}

2851 · 动物园的新朋友

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public class Animal {
    private String name,type;
    private int age;
    public void setAnimalMessage(String name, String type, int age) {
        this.name = name;
        this.type = type;
        this.age = age;
    }

    public void printAnimalMessage() {
		System.out.println(name+" is a "+type+" and is "+age+" years old this year.");
    }
}

2852 · 补充 Student 类的属性和方法

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public class Student {
    // write your code here
    public static String SEX_FEMALE = "female";
    public static String SEX_MALE = "male";
    private String sex;
    public String name;
    public int age;
    public void setSex(String sex){
        this.sex = sex;
    }
    public String toString(){
        return "name = "+name+", age = "+age+", sex = "+sex;
       
    }
}

2853 · 普通单例模式

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public class SingleClass {
    public String toString() {
        return "This is a Single Instance Class.";
    }
    
    // write your code here
    //创建 SingleClass 的一个对象
    private static SingleClass instance = new SingleClass();
 
    //让构造函数为 private，这样该类就不会被实例化
    private SingleClass(){}
 
    //获取唯一可用的对象
    public static SingleClass getInstance(){
        return instance;
    }
}

2842 · 无参构造函数的使用（一）

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public class Student {
    public String name;
    public int age;
    public double height;
    
    // write your code here
    public Student(){
        this.name = "Tom";
        this.age = 20;
        this.height = 180.0;
    }
}

2843 · 无参构造函数的使用（二）

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public class Student {
    String name;
    
    public Student(String name) {
        this.name = name;
    }
    public String toString() {
        return "name = " + name;
    }
    // write your code here
    public Student() {
    }
}

2850 · 有参构造函数的使用（一）

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public class Student {
    String name;
    int age;
    public String toString() {
        return "name = " + name + ", age = " + age;
    }
    // write your code here
    public Student(String name, int age){
        this.name=name;
        this.age=age;
    }
      public Student(String name){
        this.name=name;
        
    }
       public Student( int age){
        this.age=age;
        
    }

    public Student(){
        
    }
}

2212 · 编写对象属性的赋值方法和打印方法

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public class Employee {
    String name;
    String occupation;
    String telephone;
    int age;
    int salary;
    // write your code here
    public Employee() {

    }

    public Employee(String name, 
                    String occupation,
                    String telephone,
                    int age,
                    int salary) {
        this.name = name;
        this.occupation = occupation;
        this.telephone = telephone;
        this.age = age;
        this.salary = salary;
    }

    public void setName(String name) {
        this.name =  name;
    }
    
    public void setOccupation(String occupation) {
        this.occupation = occupation;
    }

    public void setTelephone(String telephone) {
        this.telephone = telephone;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public void setSalary(int salary) {
        this.salary = salary;
    }

    @Override
    public String toString() {
        return "Name: "+ name + System.lineSeparator() +
        "Age: "+ age + System.lineSeparator() +
        "Telephone: " + telephone + System.lineSeparator() +
        "Occupation: " + occupation + System.lineSeparator() +
        "Salary: " + salary;
    }

    public void printInfo() {
        System.out.println(toString());
        
    }
}

2614 · 求长方形的周长和面积

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class Rectangle {
    // Write your code here
    private int length;
    private int width;
    public Rectangle(int length,int width){
        this.length=length;
        this.width=width;
    }

    public void show(){
        float zhouchang=(length+width)*2;
        float mianji=length*width;
        String s="周长为: "+zhouchang+",面积为: "+mianji;
        System.out.print(s);
    }
}

2244 · 打印工作内容

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# Java 面向对象进阶

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