JAVA入坑之nefu往年瑞格练习1

目录

题目一text1464

题目二text7183

题目三text7184

题目四text7185

题目五text7186

题目六text7193

题目七text7194

 题目八text7195

题目九text7197

 题目十text7196

---

题目一text1464

import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int [][]a = new int[4][4];
        for(int i = 0;i < 4;i++)
            for(int j = 0;j < 4;j++){
                a[i][j] = input.nextInt();
            }
        int maxn = a[0][0];
        int maxi = 0, maxj = 0;
        for(int i = 0; i < 4; i ++) {
            for(int j = 0; j < 4; j ++) {
                if(maxn < a[i][j]) {
                    maxn = a[i][j];
                    maxi = i;
                    maxj = j;
                }
            }
        }
        System.out.println("max="+maxn);
        System.out.println("x=" + maxi + " y=" + maxj);
    }
}

题目二text7183

import java.util.Scanner;
import java.util.stream.IntStream;

public class Main {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        int[] arr = {input.nextInt(), input.nextInt(), input.nextInt()};
        IntStream.of(arr)
                .sorted()
                .forEach(num -> System.out.print(num + " "));
    }
}

这里，我们将整数数组转换为一个IntStream对象，然后使用sorted()方法将它们进行排序。最后，我们使用forEach()方法遍历排序后的流中的每个元素，并将它们打印到标准输出中。

题目三text7184

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        // 读取用户输入的形状
        System.out.print("请输入形状（圆形或矩形）：");
        String shape = input.next();
        if (shape.equals("圆形")) {
            // 如果是圆形，读取半径，并计算面积
            System.out.print("请输入半径：");
            double radius = input.nextDouble();
            double area = Math.PI * radius * radius;
            System.out.println("圆形的面积为：" + area);
        } else if (shape.equals("矩形")) {
            // 如果是矩形，读取长和宽，并计算面积
            System.out.print("请输入长：");
            double length = input.nextDouble();
            System.out.print("请输入宽：");
            double width = input.nextDouble();
            double area = length * width;
            System.out.println("矩形的面积为：" + area);
        } else {
            // 如果不是圆形也不是矩形，输出错误信息
            System.out.println("输入错误，只能输入圆形或矩形。");
        }
    }
}

 优化

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);

        // 读取用户输入的形状
        System.out.print("请输入形状（圆形或矩形）：");
        String shape = input.next();

        try {
            switch (shape) {
                case "圆形":
                    // 如果是圆形，读取半径，并计算面积
                    System.out.print("请输入半径：");
                    double radius = input.nextDouble();
                    double area = Math.PI * radius * radius;
                    System.out.println("圆形的面积为：" + area);
                    break;

                case "矩形":
                    // 如果是矩形，读取长和宽，并计算面积
                    System.out.print("请输入长：");
                    double length = input.nextDouble();
                    System.out.print("请输入宽：");
                    double width = input.nextDouble();
                    area = length * width;
                    System.out.println("矩形的面积为：" + area);
                    break;

                default:
                    // 如果不是圆形也不是矩形，输出错误信息
                    throw new IllegalArgumentException("输入错误，只能输入圆形或矩形。");
            }
        } catch (Exception e) {
            // 捕获异常并输出错误信息
            System.out.println(e.getMessage());
        }
    }
}

题目四text7185

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        // 读取用户输入的形状
        System.out.print("输入一个大于1正整数n：");
        int n = input.nextInt();
        if(n <= 1)
            System.out.println("输入n不是大于1正整数");
        else {
            for (int i = 1; i <= n; i++) {
                if (isPrime(i))
                    System.out.print(i + " ");
            }
        }
    }
    public static boolean isPrime(int n){
        if(n <= 1)
            return false;
        if(n == 2){
            return true;
        }
        for(int i = 2;i <= Math.sqrt(n);i++)
            if(n % i == 0)
                return false;
        return true;
    }
}

优化

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        System.out.print("输入一个大于1正整数n：");
        int n;
        try {
            n = scanner.nextInt();
            if (n <= 1) {
                throw new Exception("输入n不是大于1正整数");
            }
            System.out.print("n以内的素数为：");
            for (int i = 2; i <= n; i++) {
                if (isPrime(i)) {
                    System.out.print(i + " ");
                }
            }
        } catch (Exception e) {
            System.out.println("错误：" + e.getMessage());
        }
    }

    public static boolean isPrime(int n) {
        if (n < 2) {
            return false;
        }
        for (int i = 2; i <= Math.sqrt(n); i++) {
            if (n % i == 0) {
                return false;
            }
        }
        return true;
    }
}

题目五text7186

import java.util.Scanner;

public class Main{
    public static void main(String[] args) {
        int[] array = {-2, 1, 4, 5, 8, 12, 17, 23, 45, 56, 90, 100};
        Scanner in = new Scanner(System.in);
        System.out.print("输入一个整数n：");
        int n = in.nextInt();
        int flag = 1;
        for(int i = 0; i < 12; i ++) {
            if(n == array[i]) {
                System.out.println(n + "是数组中的第" + i + "个元素");
                flag = 0;
                break;
            }
        }
        if(flag == 1) {
            System.out.println(n + "不在数组中");
        }
    }
}

 优化

import java.util.Arrays;
import java.util.Scanner;

public class Main {
    private static final int[] ARRAY = {-2, 1, 4, 5, 8, 12, 17, 23, 45, 56, 90, 100};
    private static final int ARRAY_LENGTH = ARRAY.length;
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.print("输入一个整数n：");
        int n = in.nextInt();
        int index = Arrays.binarySearch(ARRAY, n);
        if (index >= 0) {
            System.out.println(n + "是数组中的第" + (index + 1) + "个元素");
        } else {
            System.out.println(n + "不在数组中");
        }
    }
}

题目六text7193

​
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
       Scanner input = new Scanner(System.in);
       double f = input.nextDouble();
       double c = 5 * (f - 50) / 9 + 10;
       System.out.printf("The temperature is %.2f.", c);
    }
}

​

优化

import java.util.InputMismatchException;
import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        double f = 0;
        try {
            f = input.nextDouble();
        } catch (InputMismatchException e) {
            System.out.println("Invalid input. Please enter a number.");
            return;
        }
        double c = 5 * (f - 50) / 9 + 10;
        System.out.printf("The temprature is​ %.2f.",c);
    }
}

题目七text7194

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int repeat = sc.nextInt();
        for (int i = 0; i < repeat; i++) {
            int a = sc.nextInt();
            int n = sc.nextInt();
            long sum = 0;
            long base = 1; 
            for (int j = 1; j <= n; j++) {
                sum += base * a;
                base = base * 10 + 1;
            }
            System.out.println(sum);
        }
    }
}
​

 题目八text7195

import java.util.Arrays;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.print("输入一个四位整数n：");
        int n = in.nextInt();
        int digit1 = n % 100;
        int digit2 = n / 10 % 10;
        int digit3 = n / 100 % 10;
        int digit4 = n / 1000;
        digit1 = (digit1 + 9) % 10;
        digit2 = (digit2 + 9) % 10;
        digit3 = (digit3 + 9) % 10;
        digit4 = (digit4 + 9) % 10;
        int number =  digit2 * 1000 + digit1 * 100 + digit4 * 10 + digit3;
        System.out.println("The encrypted number is " + number);

    }
}

优化

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        System.out.print("输入一个四位整数n：");
        int n = in.nextInt();
        int[] digits = new int[4];
        digits[0] = n % 10;
        digits[1] = n / 10 % 10;
        digits[2] = n / 100 % 10;
        digits[3] = n / 1000;

        for (int i = 0; i < 4; i++) {
            digits[i] = (digits[i] + 9) % 10;
        }

        int encryptedNumber = digits[2] * 1000 + digits[1] * 100 + digits[0] * 10 + digits[3];
        System.out.printf("加密后的数字为：%04d", encryptedNumber);
    }
}

题目九text7197

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int repeat = sc.nextInt();
        for (int i = 0; i < repeat; i++) {
            int a = sc.nextInt();
            int n = sc.nextInt();
            long sum = 0;
            long base = 1; 
            for (int j = 1; j <= n; j++) {
                sum += base * a;
                base = base * 10 + 1;
            }
            System.out.println(sum);
        }
    }
}
​

 题目十text7196

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {

        int n;

		Scanner scanner = new Scanner(System.in);
		n = scanner.nextInt();

	    //write your code
		int flag = -1;
		double num = 0.0f;
		double numerator; // 分子
		double denominator; //分母
		for(int i = 1; i <= n; i ++) {
			
			flag = flag * (-1);
			numerator = flag;
			denominator = (i-1) * 3 + 1;
			num = num + (numerator / denominator);
			
		}
		System.out.println(num);
	}
}