Java程序:生成圣诞树:格式化？

Question

所以在我的CS课上，我们有一个小的hw问题，这个问题在一个星期左右才到期，除了一小部分外，它几乎是有效的。这是一项任务：

编写一个名为ChrisTree的程序，生成圣诞树的图像作为输出。它应该有一个包含两个参数的方法:一个表示树中的段数，另一个表示每个段的高度。例如，左边的树有三段高4，右边的树有两段高5。

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因此，我的代码可以工作，除非在一些树上，树的最后一行和树干都由一个空格隔开。我似乎不能不做一个新的洞就把那个洞堵住。有没有人看到这个问题的“根源”？树段和树高是通过改变类常量而变化的(我知道，这是改变类常量的糟糕方法，但这正是这个人想要的)(我知道它可能也是可怕的冗余)。

public class ChrisTree {
  public static final int SEGMENTS = 4;
  public static final int HEIGHT = 4;
  public static void main(String[] args){
  makeTree();
  }
  // makeTree: code that prints the tree; params: num. of segments of tree, height of tree segments
  public static void makeTree(){
  // maxStars: calculation the length of each line which is the sum of spaces and stars for any line
    int maxStars = 2*HEIGHT+2*SEGMENTS-3;
    // maxStr: master variable string that will be changed and printed for each line
    String maxStr = "";
    // populates maxStr will spaces; will be used with substring to generate needed spaces
    for (int len=0; len < maxStars; len++){
      maxStr+=" ";
    }
    // loops once per segment
    for (int i=1; i <= SEGMENTS; i++){
      // starStr: variable string that changes perline that holds the stars

      // populates starStr with stars
      // loops through each line
      for (int line=1; line <= HEIGHT; line++){
        String starStr = "";
        for (int j=1; j <= 2*line+2*i-3; j++){
          starStr+="*";
        }
        for (int space=0; space <= maxStars-(HEIGHT+line+i); space++){
          starStr = " " + starStr;
        }
        System.out.println(starStr);
      }
    }

    for (int i=0; i <= maxStars/2;i++){
      System.out.print(" ");
    }
    System.out.print("*\n");
    for (int i=0; i <= maxStars/2;i++){
      System.out.print(" ");
    }
    System.out.print("*\n");
    for (int i=0; i <= maxStars/2-3;i++){
      System.out.print(" ");
    }
    System.out.print("*******\n");
  }
}

Answer 1

作为我对做作业问题的辩护，这里的解决方案太伤我的眼睛了。(我知道这是标准的家庭作业问题，我早在80年代就在帕斯卡做过。)

package com.edwinbuck.christmas;

/**
 * Draws a ChristmasTree.

 * @author Edwin Buck
 */
public class ChristmasTree {

    public static final int SEGMENTS = 4;
    public static final int HEIGHT = 4;

    public static void main(String[] args) {
        int maxSize = 1 + 2 * (SEGMENTS - 1) + 2 * (HEIGHT - 1);
        // for each segment beyond zero, we need 2 more asterisks.
        for (int segmentContrib = 0; segmentContrib < 2 * SEGMENTS; segmentContrib += 2) {
            // for each segment slice beyond zero, we need 2 more asterisks.
            for (int sliceContrib = 0; sliceContrib < 2 * HEIGHT; sliceContrib += 2) {
                drawCentered(maxSize, 1 + segmentContrib + sliceContrib);
            }
        }
        // draw the trunk
        drawCentered(maxSize, 1);
        drawCentered(maxSize, 1);
        // draw the base
        drawCentered(maxSize, 7);
    }

    /**
     * Draws a line of asterisks, centered within size spaces.
     *
     * @param size The size to center on.
     * @param asterisks The number of asterisks to draw.
     */
    private static void drawCentered(int size, int asterisks) {
        int before = (size - asterisks) / 2;
        int after = size - before - asterisks;
        print(before, " ");
        print(asterisks, "*");
        print(after, " ");
        System.out.println();
    }

    /**
     * Draws a character a number of times.
     *
     * @param count The number of time to draw the character.
     * @param character The character to draw.
     */
    private static void print(int count, final String character) {
        for (int i = 0; i < count; i++) {
            System.out.print(character);
        }
    }

}

关键是要认识到，所有的线条都是大小可变的星号中心。一旦您这样做，那么您只需要计算出循环来绘制节(和最大行大小)。

最大行大小由最下面的部分控制。每个输入(SEGMENTS和HEIGHT)都需要从“计数从1”转换为“从0计数”。每个额外的段添加两个星号大小，每个额外的切片也是如此。这棵树必须至少有一个星号，其中一个(树干)沿着中心运行。这就引出了公式

 1 + 2*(SEGMENTS-1) + 2(HEIGHT-1)

许多人已经简化为

 2*SEGMENTS + 2*HEIGHT - 3

我没有简化它，因为它隐藏了意图，这在代码中一旦丢失就很难恢复。

然后，在遍历循环时，我决定让贡献者将大小增加2。它使其余的数学更容易，因为我们不必把“魔术”公式和数学在奇怪的地方。这意味着我们可以使用参数drawCentered(...)重用我们的1 + segmentContrib + sliceContrib，其中其他两个变量是段和切片“星号”贡献。

最后，我们画了一个树干两个垂直星号和底部。

Answer 2

我知道现在已经很晚了，但我只是写了这篇文章，它起了作用。

public class ChrisTree {
    public static final int SEGMENTS = 4;
    public static final int HEIGHT = 4;

    public static void main(String[] args) {
        makeTree();
    }

    public static void makeTree() {
        int maxStars = 2 * HEIGHT + 2 * SEGMENTS - 3;
        String maxStr = "";
        for (int l = 0; l < maxStars; l++) {
            maxStr += " ";
        }
        for (int i = 1; i <= SEGMENTS; i++) {
            for (int line = 1; line <= HEIGHT; line++) {
                String starStr = "";
                for (int j = 1; j <= 2 * line + 2 * i - 3; j++) {
                    starStr += "*";
                }
                for (int space = 0; space <= maxStars - (HEIGHT + line + i); space++) {
                    starStr = " " + starStr;
                }
                System.out.println(starStr);
            }
        }

        for (int i = 0; i <= maxStars / 2; i++) {
            System.out.print(" ");
        }
        System.out.println(" " + "*" + " ");
        for (int i = 0; i <= maxStars / 2; i++) {
            System.out.print(" ");
        }
        System.out.println(" " + "*" + " ");
        for (int i = 0; i <= maxStars / 2 - 3; i++) {
            System.out.print(" ");
        }
        System.out.println(" " + "*******");
    }
}