牛客网：NC103 反转字符串

1.使用临时数组解决

import java.util.*;


public class Solution {
    
    public String solve (String str) {
        // write code here
        if (str == null || str.length() == 0 ){
            return "";
        }
        char[] ans = new char[str.length()];
        
        for (int i = 0; i < str.length(); i++){
            ans[str.length() - i - 1] = str.charAt(i);
        }
        return String.valueOf(ans);
    }
}

2.使用双指针

public class Solution {

    public static void main(String[] args) {
        Solution solution = new Solution();

    }

    public String solve (String str) {
        // write code here
        if (str == null || str.length() == 0){
            return "";
        }
        int left = 0;
        int right = str.length() - 1;

        char[] chars = str.toCharArray();

        while (left <= right){
            char temp = str.charAt(left);
            chars[left++] =  str.charAt(right);
            chars[right--] = temp;
        }
        return String.valueOf(chars);
    }
}