在Java中，如何使用嵌套的for循环编写一个星号金字塔？

huangapple
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英文:

In Java, how would I code a pyramid of asterisks by using nested for loops?

问题

  1. 我正在处理一个作业，需要使用嵌套循环编写一个侧倾的星号金字塔程序。
  2. 这个程序的输出应该类似这样：

**

**
*

  2. 当我运行我的程序时，它只显示代码的最后四行。我不知道前面的三行为什么没有显示出来。
  3. 这是我的代码：

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

  1.     for(int a = 0; a < 8; a++) //1
  2.     {
  3.         if(a < 4){
  4.             for(int b = a; b < 4; b++)
  5.             {
  6.                 System.out.print("*");
  7.             }
  8.             
  9.         }
  10.         if(a >= 4)
  11.             for(int c = a; c < 4; c++)
  12.             {  
  13.                 System.out.print("*");
  14.             }
  15.         
  16.         System.out.println();
  17.     } //loop 1
  18.     
  19. }

}

  2. 这是我的输出：

**
*

  1. （输出后面有一些空格，我没有包含在内。这是因为外部循环迭代了八次。）如何使我的程序正确显示所有代码，而不仅仅是最后四行？
  3. 非常感谢您的帮助。
英文:

I am working on an assignment where I have to use nested loops to program a pyramid of asterisks that is on its side.
The output of this program should look like this:

  1. *    
  2. **    
  3. ***    
  4. **** 
  5. ***
  6. **
  7. *

When I run my program, it only displays the final four lines of the code. I don't know why the first three don't show up.
Here is my code:

  1. public class Main
  2. {
  3. 	public static void main(String[] args) {
  4. 		
  5. 		for(int a = 0; a &lt; 8; a++) //1
  6. 		{
  7. 		    if(a &lt; 4){
  8. 		        for(int b = a; b &lt; 4; b++)
  9. 		        {
  10. 		            System.out.print(&quot;*&quot;);
  11. 		        }
  12. 		        
  13. 		    }
  14. 		    if(a &gt;= 4)
  15. 		        for(int c = a; c &lt; 4; c++)
  16. 		        {  
  17. 		            System.out.print(&quot;*&quot;);
  18. 		        }
  19. 		    
  20. 		    System.out.println();
  21. 		} //loop 1
  22. 		
  23. 	}
  24. }

And here is my output:

  1. ****
  2. ***
  3. **
  4. *

(There is some empty space after the output that I did not include. This is caused by the outer for loop iterating eight times.) How would I make my program correctly display all of the code, instead of just the last four lines?

Any help would be greatly appreciated.

答案1

得分: 1

在你的逻辑中有几个错误：

  1. 由于你只需要 7 行，第一个循环应该迭代直到 a < 7
  2. 在前 3 行中，你的嵌套循环应该从 0 迭代到 a
  3. 此后，另一个嵌套循环应该从 a 迭代到 7
  4. 最好使用 if-else 语句替代两个 if 语句

以下是我测试过的完整解决方案：

  1. for (int a = 0; a < 7; a++) {
  2.      if (a < 4) {
  3.           for (int b = 0; b <= a; b++)
  4.                System.out.print("*");
  5.      } else {
  6.           for (int c = a; c < 7; c++)
  7.                System.out.print("*");
  8.      }
  9.      System.out.println();
  10. }

输出：

  1. *
  2. **
  3. ***
  4. ****
  5. ***
  6. **
  7. *

编辑：

正如在评论中提到的，你还可以将外部循环拆分成两部分，以消除条件，代码如下：

  1. for (int a = 0; a < 4; a++) {
  2.      for (int b = 0; b <= a; b++)
  3.           System.out.print("*");
  4.      System.out.println();
  5. }
  6. for (int a = 4; a <= 7; a++) {
  7. 	 for (int b = a; b < 7; b++)
  8. 	   	  System.out.print("*");
  9. 	 System.out.println();
  10. }
英文:

There are several mistakes in your logic:

  1. Since you only need 7 rows, the first loop should iterate until a &lt; 7
  2. In the first 3 rows, your nested loop should iterate from 0 to a
  3. After that, the other nested loop should go from a to 7
  4. It is better to use if-else instead of two if statements

Here is the complete solution that I tested:

  1. for(int a = 0; a &lt; 7; a++) {
  2.      if(a &lt; 4){
  3.           for(int b = 0; b &lt;= a; b++)
  4.                System.out.print(&quot;*&quot;);
  5.      }else {
  6.           for(int c = a; c &lt; 7; c++)
  7.                System.out.print(&quot;*&quot;);
  8.      }
  9.      System.out.println();
  10. }

Output:

  1. *
  2. **
  3. ***
  4. ****
  5. ***
  6. **
  7. *

EDIT:

As mentioned in the comments, you can also split the outer loop into two parts in order to remove the conditions as follows:

  1. for(int a = 0; a &lt; 4; a++) {
  2.      for(int b = 0; b &lt;= a; b++)
  3.           System.out.print(&quot;*&quot;);
  4.      System.out.println();
  5. }
  6. for(int a = 4; a &lt;= 7; a++) {
  7. 	 for(int b = a; b &lt; 7; b++)
  8. 	   	  System.out.print(&quot;*&quot;);
  9. 	 System.out.println();
  10. }

答案2

得分: 0

你很接近了。尝试类似这样的代码：

  1. int size = 4;
  3. for (int line = 1; line < size * 2; line++) {
  4.   if (line <= size) {
  5.     for (int i = 0; i < line; i++) {
  6.       System.out.print("*");
  7.     }
  8.   } else {
  9.     for (int i = 0; i < size * 2 - line; i++) {
  10.       System.out.print("*");
  11.     }
  12.   }
  13.   System.out.println();
  14. }
英文:

You're close. Try something like this:

  1. int size = 4;
  2. 		
  3. for(int line = 1; line &lt; size * 2; line++) {
  4.   if(line &lt;= size) {
  5.     for(int i = 0; i &lt; line; i++) {
  6.       System.out.print(&quot;*&quot;);
  7.     }
  8.   }
  9.   else {
  10.     for(int i = 0; i &lt; size * 2 - line; i++) {
  11.       System.out.print(&quot;*&quot;);
  12.     }
  13.   }
  14.   System.out.println();
  15. }

huangapple
  • 本文由 发表于 2020年5月30日 05:49:29
  • 转载请务必保留本文链接：https://go.coder-hub.com/62095080.html
  • java
  • loops
  • nested-loops
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