以错误顺序打印三角形字符以及不需要的字符

Question

该程序的目的是让用户决定三角形的长度（行），并决定它应该朝上还是朝下。和三角形是由字母，所以它应该是这个样子：

How many rows would you like? (finish with -1): 4 
Do you want the triangle to face up (1) or down (2)? 1 

A 
A B 
A B C 
A B C D 

How many rows would you like? (finish with -1): 6 
Do you want the triangle to face up (1) or down (2)? 2 

A B C D E F 
A B C D E 
A B C D 
A B C 
A B 
A 

我有两个问题，当我试图让三角打印面朝下，第一个字母是这样的（它应该开始与一个）

F E D C B A 
F E D C B 
F E D C 
F E D 
F E 
F 

而字母后面加载我不想要的不同字符的负载。我尝试了很多东西，似乎没有任何工作。我真的可以使用一些建议。

这是我到目前为止的代码：

import java.util.Scanner; 

public class Triangle { 

    public static void main(String args[]) { 
     Scanner scan = new Scanner(System.in); 
     int a = 0; 
     int b = 0; 

     while (a != -1) { 
      System.out.println("How many rows would you like? (finish with -1):"); 
      a = scan.nextInt(); 
      if (a != -1) { 
       b = a - 1; 

       int j = 'A'; 
       char alphabet = (char) (j + 'A'); 


       System.out.println("Do you want the triangle to face up (1) or down (2)?"); 
       int c = scan.nextInt(); 

       if (c == 1) { 
        for (int i = 1; i <= b + 'A'; i++) { 
         for (j = 'A'; j <= i; j++) 
          System.out.print((char) j + " "); 
         System.out.println(alphabet); 
        } 
       } else { 
        for (int i = 1; i <= b + 'A'; i++) { 
         for (j = b + 'A'; j >= i; j--) 
          System.out.print((char) j + " "); 
         System.out.println(alphabet); 

        } 
       } 
      } 
     } 
    } 

} 

Answer 1

public static void main(String[] args) { 
    Scanner scan = new Scanner(System.in); 
    int a = 0; 
    int b = 0; 

    while (a != -1) { 
     System.out.println("How many rows would you like? (finish with -1):"); 
     a = scan.nextInt(); 
     if (a != -1) { 
      System.out.println("Do you want the triangle to face up (1) or down (2)?"); 
      int c = scan.nextInt(); 

      if (c == 1) { 
       for (int i = 0; i < a; i++) { 
        for (int j = 0; j <= i; j++) { 
         System.out.print((char) (j + 'A')); 
        } 
        System.out.println(); 
       } 
      } else { 
       for (int i = 0; i < a; i++) { 
        for (int j = a; j > i; j--) { 
         System.out.print((char) (a - j + 'A')); 
        } 
        System.out.println(); 
       } 
      } 
     } 
    } 
} 

Answer 2

采用下面给出一个更加模块化的解决方案。 它打印由四行组成的三角形，一个朝上，另一个朝下。

public static void main(String args[]) { 
    int a = 4; // # of rows 
    // Triangle facing up 
    for (int i = 1; i <= a; i++) // i - How many letters in this row (also row No) 
    printRow(i); 
    System.out.println("--------"); // Separator 
    // Triangle facing down - Start from the longest row, then decrease its length 
    for (int i = a; i > 0; i--) 
    printRow(i); 
} 

static void printRow(int length) { 
    for (int j = 0; j < length; j++) // j - char code shift 
    System.out.printf("%c ", j + 'A'); 
    System.out.println(); 
} 

该解决方案更优雅，因为打印行的代码不会重复。

还要注意一种更自然的方式来表示连续行的长度：对于朝下的三角形减少了行长度。