344. reverse string

Write a function that reverses a string. The input string is given as an array of characters char[].

Do not allocate extra space for another array, you must do this by modifying the input array in-place with O(1) extra memory.

You may assume all the characters consist of printable ascii characters.

Example 1:

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Input: ["h","e","l","l","o"]
Output: ["o","l","l","e","h"]

Example 2:

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Input: ["H","a","n","n","a","h"]
Output: ["h","a","n","n","a","H"]

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class  {
    public String reverseString(String s) {
        if (s == null || s.length() == 0) return s;
      StringBuilder sb = new StringBuilder();
        for (int i = s.length() - 1; i >= 0; i--) {
          sb.append(s.charAt(i));
        }
        return sb.toString();
    }
}