[Java] 자바의 정석 / chap5.배열_연습문제

5-3)

package j04_Array;

public class Ex_example {

	public static void main(String[] args) {
		int[] arr = {10, 20, 30, 40, 50};
		int sum = 0;
		
		for (int i = 0; i < arr.length; i++) {
			sum += arr[i];
		}
		
		System.out.println(sum);
		
		
	}

}

 

 

 

5-4)

package j04_Array;

public class Ex_example {

	public static void main(String[] args) {
		int[] [] arr = {
				{5, 5, 5, 5, 5},
				{10, 10, 10, 10, 10},
				{20, 20, 20, 20, 20},
				{30, 30, 30, 30, 30}
		};
		
		int total = 0;
		float average = 0;
		
		for (int i = 0; i < arr.length; i++) {
			for (int j = 0; j < arr[0].length; j++) {
				total += arr[i][j];
			}
		}
		
		average = (float)total / (arr.length * arr[0].length);
		
		System.out.println("total => " + total);
		System.out.println("average => " + average);
		
		
	}

}

 

 

 

5-5)

package j04_Array;

public class Ex_example {

	public static void main(String[] args) {
		int[] ballArr = { 1, 2, 3, 4, 5, 6, 7, 8, 9 };
		int[] ball3 = new int[3];

		for (int i = 0; i < ballArr.length; i++) {
			int j = (int) (Math.random() * ballArr.length);
			int tmp = 0;

			tmp = ballArr[i];
			ballArr[i] = ballArr[j];
			ballArr[j] = tmp;
		}

		System.arraycopy(ballArr, 0, ball3, 0, 3);

		for (int i = 0; i < ball3.length; i++) {
			System.out.print(ball3[i]);
		}

	}

}

 

 

 

5-6)

package j04_Array;

import java.util.Scanner;

public class Ex_example {

	public static void main(String[] args) {
		String[] words = {"television", "computer", "mouse", "phone"};
		
		Scanner scanner = new Scanner(System.in);
		
		for (int i = 0; i <words.length; i++) {
			char[] question = words[i].toCharArray();
			
			char randomNum = (char)((int)(Math.random() * question.length));
			char temp = ' ';
			
			temp = question[i];
			question[i] = question[randomNum];
			question[randomNum] = temp;
			
			System.out.printf("Q%d. %s의 정답을 입력하세요. > ", i + 1, new String(question));
			
			String answer = scanner.nextLine();
			
			if (words[i].equals(answer.trim())) {
				System.out.printf("맞았습니다. %n%n");
			} else {
				System.out.printf("틀렸습니다. %n%n");
			}
			
		}

	}

}

..................섞여서 나오긴 하는데 다시 생각해봐야 할 것 같다.....

 

 

 

 

+ 추가)

아니 나 바보야???????????????????? 왜 randomNum을 char로 받음?????????

어이 아리마셍

 

package j04_Array;

import java.util.Scanner;

public class Ex_example {

	public static void main(String[] args) {
		String[] words = {"television", "computer", "mouse", "phone"};
		
		Scanner scanner = new Scanner(System.in);
		
		for (int i = 0; i < words.length; i++) {
			char[] question = words[i].toCharArray();
			
			int num = (int)(Math.random() * question.length);
			char temp;
			
			for (int j = 0; j < question.length; j++) {
				temp = question[j];
				question[j] = question[num];
				question[num] = temp;
			}
			
			System.out.printf("Q%d. %s의 정답을 입력하세요. > ", i + 1, new String(question));
			
			String answer = scanner.nextLine();
			
			if (words[i].equals(answer.trim())) {
				System.out.printf("맞았습니다. %n%n");
			} else {
				System.out.printf("틀렸습니다. %n%n");
			}
			
		}

	}

}