java - 递归方法返回一个字符串逆序需要String和Index位置作为参数

Question

我正在尝试使用递归来反转字符串，但特殊之处在于我必须从指定索引开始返回该索引中包含的字符，然后反转该索引后的剩余字符串并将两者合并为一个输出。我尝试这样做，有时它会给出数组越界异常，有时最终会出现比应有的字母更多的字母，例如hellooo的测试结果为lloooooo。任何有关调整此代码的帮助将不胜感激，因为当我知道需要第二个参数时，我真的迷失了。

  public class ReverseTest
    {
        public static void main(String[] argv) 
        {
            System.out.println(reverse("a", 0));
            System.out.println(reverse("hi", 0));
            System.out.println(reverse("helloooo", 2));
        }


        public final static String reverse(String s, int ind)
        {
            int length = s.length(); //get string length

            if (length <= 1) //if length is 1 or lower just repeat the string nothing to do
                return s; //return string
            else //if we have something to work with...
                return s.substring(ind) + reverse(s.substring(ind + 1, length - 1), ind); //return substring of necessary index + reverse the rest and display in one string
        }
    }

Answer 1

不确定您的版本有什么问题，但我根据我认为直观的实现构建了自己的版本:

private static String reversePartially(String initial, int target) {
    return reversePartially(initial, target, target);
}

private static String reversePartially(String initial, int index, int target) {
    // if we are at the target index put the character at the front
    if(index == target) return initial.charAt(target) + reversePartially(initial, index + 1, target);
    // if we are in the second part return the characters reversed
    if(index > target) return reversePartially(initial, index + 1, target) + initial.charAt(index);
    // base condition
    if(index == initial.length()) return "";
    return "";
}