java - 如何在java中繪制帶星號的半箭頭？

Question

我在我的第一個 java 類中，我正在嘗試使用星號繪制一個半箭頭。 我應該使用嵌套循環，其中內部循環繪制 *s 並且外部循環迭代的次數等於箭頭底部的高度。 我學習了 if-else、while 循環和 for 循環。

到目前為止，我已經能夠正確繪制輸入值的箭頭
箭底高度：5
箭頭底寬：2
箭頭寬度：4

當我嘗試添加一個while循環作為外循環時，程序超時。 我很茫然。

我需要使用的下一個輸入是 2、3、4。我的代碼獲取右下角 (2) 的高度，而不是寬度。

我需要的最后一個輸入是 3、3、7。我的代碼根本不正確。 這就是我到目前為止所擁有的。

我應該使用什么樣的循環來獲得正確的寬度？

  Scanner scnr = new Scanner(System.in);
  int arrowBaseHeight = 0;
  int arrowBaseWidth  = 0;
  int arrowHeadWidth = 0;
  int i = 0;

  System.out.println("Enter arrow base height: ");
  arrowBaseHeight = scnr.nextInt();

  System.out.println("Enter arrow base width: ");
  arrowBaseWidth = scnr.nextInt();

  System.out.println("Enter arrow head width: ");
  arrowHeadWidth = scnr.nextInt();


  for (i = 1; i <= arrowBaseHeight; ++i) {
      // Draw arrow base (height = 3, width = 2)
      System.out.println("**");
  }

  // Draw arrow head (width = 4)
  System.out.println("****");
  System.out.println("***");
  System.out.println("**");
  System.out.println("*");

輸出箭頭的外觀示例：

**
**
**
**
****
***
**
*

Answer 1

您必須制作兩個嵌套循環。 內循環將打印單行字符，外循環將打印多行。

這是您使用“for”循環的問題的解決方案。

//printing arrow base
for (int h = 0; h < arrowBaseHeight; ++h)
{
  //printing single line - every line is the same
  for(int w = 0; w < arrowBaseWidth; w++)
    System.out.print("*");
  //finishing line
  System.out.println();
}

//printing arrow head
//starting with provided width and decreasing it with every iteration
for (int a = arrowHeadWidth; a > 0 ; a--)
{
  //printing single line - now every line is different
  //you have to count how many asterisks you are printing
  for(int i = 0; i < a; i++)
    System.out.print("*");
  //finishing line
  System.out.println();
}

如果它們只包含一行，則不需要在循環中使用括號。 例如：

for(int i = 0; i < a; i++)
    System.out.print("*");

相當於：

for(int i = 0; i < a; i++)
{
    System.out.print("*");
}

Answer 2

可以使用兩個作為第一個來打印輸入寬度的行數，使用子字符串方法來捕獲打印量*

然后第二次打印箭頭的頭部並減小箭頭的寬度

for (int i = 0;i < arrowBaseHeight; i++) 
 //when there is more than one instruction within a structure can be written without {}
    System.out.println("*************************".substring(0, arrowBaseWidth));

System.out.println("");
for (int i = arrowHeadWidth; i>=0; i-=1)  // head
    System.out.println("*************************".substring(0, i));

Answer 3

對於這個問題，你會想要使用 for 循環，因為你知道它應該重復的確切次數。 您知道這一點是因為用戶輸入了箭頭每個部分的大小。

Scanner scnr = new Scanner(System.in);

int arrowBaseHeight = 0;
int arrowBaseWidth  = 0;
int arrowHeadWidth = 0;
int i = 0;

System.out.println("Enter arrow base height: ");
arrowBaseHeight = scnr.nextInt();

System.out.println("Enter arrow base width: ");
arrowBaseWidth = scnr.nextInt();

System.out.println("Enter arrow head width: ");
arrowHeadWidth = scnr.nextInt();

//Your code above | Below is the modified code

String ast = ""; //String ast will contain how many asterisk we want for the base width;

for (int x = 1; x <= arrowBaseWidth; x++) //Loop forms the base width of the arrow
{
    ast += "*"; //This adds as many asterisks as we need to make the base width. SO if they enter 4, we get 4 *;
}


for (i = 1; i < arrowBaseHeight; ++i) 
{   
    System.out.println(ast); //Prints out the base width, which is now a String object
}

int tempHeadWidth = arrowHeadWidth; //Added this tempHeadWidth variable since we will be modifying it directly and 
                                    //we don't want to modify the original data and variable (it will cause problems if we do.

for (int y = 1; y <= arrowHeadWidth; y++) 
{
    for(int z = tempHeadWidth; z > 0; z--) //This loop prints the amount of asterisks we need per line in the arrowHead
    {
        System.out.print("*");
    } 
    // Once the loop above is finished, the rest of the code will execute in the main for-loop and then scheck if it will run again.
    tempHeadWidth -= 1; //So we are lowering the tempHeadWidth by one so the next time it enters 
                        //the nested (2nd) for loop it will be one asterisk smaller

    System.out.println(); //This makes a new line to keep adding more stars for the next row 
}

此方法允許用戶為箭頭輸入任何大小（當然要保持在 int 的值邊界內）

Answer 4

我知道這有點晚了，但我正在 zybooks 上經歷同樣的挑戰（這恰好是一項實驗室活動）。 上面標記為已解決的代碼是正確的，但是我認為我會為每個人澄清一下代碼中的一些內容。 下面是我曾經100%通過的代碼，需要修改的地方我會評論。 我還使縮進更容易閱讀。 我希望這可以幫助任何需要朝着正確方向努力的人。

import java.util.Scanner; 

public class DrawHalfArrow {
   public static void main(String[] args) {
      Scanner scnr = new Scanner(System.in);
      int arrowBaseHeight = 0;
      int arrowBaseWidth  = 0;
      int arrowHeadWidth = 0;

  System.out.println("Enter arrow base height: ");
  arrowBaseHeight = scnr.nextInt();

  System.out.println("Enter arrow base width: ");
  arrowBaseWidth = scnr.nextInt();

/* The while loop below needed to be added for the user input to make sure
** that their input never exceeded that of the arrowHeadWidth */

  while (arrowHeadWidth <= arrowBaseWidth) {
     System.out.println("Enter arrow head width: ");
     arrowHeadWidth = scnr.nextInt();
  }

  String ast = "";
  for (int x = 1; x <= arrowBaseWidth; x++) {
     ast+= "*";
  }

/* Here 'i' needed to be intialized as an integer ('int'). Also the '=' needed
** to be added to i<= arrowBaseHeight */

  for (int i = 1; i <= arrowBaseHeight; ++i) { 
        System.out.println(ast);
  }
  int tempHeadWidth = arrowHeadWidth;
  for (int y =1; y <= arrowHeadWidth; y++) {
     for (int z = tempHeadWidth; z > 0; z--) {
        System.out.print("*");
     }
     tempHeadWidth -= 1;
     System.out.println();
  }

  return;
   }
}

Answer 5

我的完整解決方案基於@dev joels 的回答

import java.util.Scanner; 

public class DrawHalfArrow {
   public static void main(String[] args) {
      Scanner scnr = new Scanner(System.in);
      int arrowBaseHeight = 0;
      int arrowBaseWidth  = 0;
      int arrowHeadWidth = 0;

      System.out.println("Enter arrow base height: ");
      arrowBaseHeight = scnr.nextInt();

      System.out.println("Enter arrow base width: ");
      arrowBaseWidth = scnr.nextInt();

      //System.out.println("Enter arrow head width: ");

      while (arrowHeadWidth <= arrowBaseWidth) {
        System.out.println("Enter arrow head width: ");
        arrowHeadWidth = scnr.nextInt();
      }       

      for (int h = 0; h < arrowBaseHeight; ++h) {
         for(int w = 0; w < arrowBaseWidth; w++) 
            System.out.print("*");
        System.out.println();
      }

       for (int a = arrowHeadWidth; a > 0 ; a--) {
          for(int i = 0; i < a; i++)
             System.out.print("*");
         System.out.println();
       }
      return;
   }
}

Answer 6

import java.util.Scanner; 

public class DrawHalfArrow {
   public static void main(String[] args) {
      Scanner scnr = new Scanner(System.in);
      int arrowBaseHeight;
      int arrowBaseWidth;
      int arrowHeadWidth;
      
      System.out.println("Enter arrow base height:");
      arrowBaseHeight = scnr.nextInt();
      
      System.out.println("Enter arrow base width:");
      arrowBaseWidth = scnr.nextInt();
      
      
      do {
         System.out.println("Enter arrow head width:");
         arrowHeadWidth = scnr.nextInt();
      } while (arrowHeadWidth <= arrowBaseWidth); 
      
      System.out.println("");
      
      // Draw arrow base 
      int row;
      int column;
      for (row = 0; row < arrowBaseHeight; ++row) {
         for (column = 0; column < arrowBaseWidth; ++column) {
            System.out.print("*");
         }
         System.out.println("");
      }
            
      // Draw arrow head 
      for (row = 0; row < arrowHeadWidth; ++row) {
         int thisRowWidth = arrowHeadWidth - row;
         for (column = 0; column < thisRowWidth; ++column) {
            System.out.print("*");
         }
         System.out.println("");
      }
            
   }
}