Reverse String

Two pointers left right swap elements

  public String reverse(String input) {
    char[] arr = input.toCharArray();
    int i = 0;
    int j = arr.length - 1;
    while (i < j){
      char tmp = arr[i];
      arr[i] = arr[j];
      arr[j] = tmp;
      i++;
      j--;
    }
    return new String(arr);
  }

Time comp: O(N)

Space comp: O(N)