反转字符串(双指针)

题目描述

写出一个程序，接受一个字符串，然后输出该字符串反转后的字符串。

输入 :cba
返回值 :abc

---

我们最容易想到:逆向遍历字符串实现反转

实现:

    public static  String solve(String str) {
        if (null == str || str.length() == 0 || str.length() == 1) {
            return str;
        }
        StringBuilder strBuilder = new StringBuilder();
        for (int i = str.length() - 1; i >= 0; i--) {
            strBuilder.append(str.charAt(i));
        }
        return strBuilder.toString();
    }

---

使用双指针实现字符串反转

    public static String reverseString(String str) {
        if (str == null || str.length() == 0 || str.length() == 1) {
            return str;
        }
        char[] chars = str.toCharArray();
        //指向数组首元素
        int start = 0;
        //指向数组尾元素
        int end = chars.length - 1;
        char temp;
        while (start < end) {
            //字符互换
            temp = chars[start];
            chars[start] = chars[end];
            chars[end] = temp;
            //移动索引位置
            start++;
            end--;
        }
        return String.valueOf(chars);
    }

    
    public static void main(String[] args) {
        String str = "gfedcba";
        System.out.println("字符串:" + str);
        System.out.println("反转后:" + reverseString(str));
    }

字符串:gfedcba
反转后:abcdefg

---

使用StringBuilder中reverse()对字符串进行反转
api真香

    public String solve(String str) {
        if (null == str || str.length() == 0 || str.length() == 1) {
            return str;
        }
        return new StringBuilder(str).reverse().toString();
    }