java - 递归中的无限循环

Question

我正在编写代码来输出以下模式:

000000000X
00000000XX
0000000XXX
000000XXXX
00000XXXXX
0000XXXXXX
000XXXXXXX
00XXXXXXXX
0XXXXXXXXX

(每一行应该是一个接一个。我不太确定如何在论坛上显示该模式......抱歉)

我应该在代码中使用递归循环，但我最终陷入了无限循环，我真的不明白为什么..(可以肯定我实际上从未使用过递归循环)。这是我的代码:

class Recursion {
    //recursion should stop after 9 attempts
    static int stopindex = 9;

    public static void main(String[] args) {
        //a=number of "O"s and b=number of "X"s
        int a = 9;
        int b = 1;
        recursion(a, b);
    }
    public static void recursion(int a, int b) {

        //start of recursion at index 1
        int startindex = 1;

        //stop condition of recursion
        if (startindex == stopindex)
            return;

        //printing of pattern
        for (int i = a; i > 0; i--) {
            System.out.print("O");
        }
        for (int j = 0; j < b; j++) {
            System.out.print("X");
        }
        System.out.println();

        --a;
        ++b;
        ++startindex;
        recursion(a, b);
    }
}

Answer 1

你的算法有点偏离，你不应该有静态变量，你不应该改变a，以及你的第一个for循环条件 - 我认为你想要，

public static void recursion(int a, int b) {
  // stop condition of recursion
  if (a == b) return;

  // printing of pattern
  for (int i = a - b; i > 0; i--) {
    System.out.print("O");
  }
  for (int j = 0; j < b; j++) {
    System.out.print("X");
  }
  System.out.println();

  // --a;
  ++b; // <-- this could be done in the recursion call below,
  recursion(a, b);
  // recursion(a, ++b); // <-- like that.
}

输出为

OOOOOOOOX
OOOOOOOXX
OOOOOOXXX
OOOOOXXXX
OOOOXXXXX
OOOXXXXXX
OOXXXXXXX
OXXXXXXXX