comefrom: <qiyuangong>541_Reverse_String_II_1.java
code: public String reverseStr(String s, int k) {
          char[] a = s.toCharArray();
          for (int start = 0; start < a.length; start += 2 * k) {
              int i = start, j = Math.min(start + k - 1, a.length - 1);
              while (i < j) {
                  char tmp = a[i];
                  a[i++] = a[j];
                  a[j--] = tmp;
              }
          }
          return new String(a);
      }
masked: public String var_0 ( String var_1 , int var_2 ) {
    char [ ] var_3 = var_1 . toCharArray ( ) ;
    for ( int var_4 = 0 ;
    var_4 < var_3 . length ;
    var_4 += 2 * var_2 ) {
      int var_5 = var_4 , var_6 = Math . min ( var_4 + var_2 - 1 , var_3 . length - 1 ) ;
      while ( var_5 < var_6 ) {
        char var_7 = var_3 [ var_5 ] ;
        var_3 [ var_5 ++ ] = var_3 [ var_6 ] ;
        var_3 [ var_6 -- ] = var_7 ;
      }
    }
    return new String ( var_3 ) ;
  }
  