static String prevNum ( String str ) {
  int len = str . length ( ) ;
  int index = - 1 ;
  for ( int i = len - 2 ;
  i >= 0 ;
  i -- ) {
    if ( str . charAt ( i ) > str . charAt ( i + 1 ) ) {
      index = i ;
      break ;
    }
  }
  int smallGreatDgt = - 1 ;
  for ( int i = len - 1 ;
  i > index ;
  i -- ) {
    if ( str . charAt ( i ) < str . charAt ( index ) ) {
      if ( smallGreatDgt == - 1 ) {
        smallGreatDgt = i ;
      }
      else if ( str . charAt ( i ) >= str . charAt ( smallGreatDgt ) ) {
        smallGreatDgt = i ;
      }
    }
  }
  if ( index == - 1 ) {
    return "-1" ;
  }
  if ( smallGreatDgt != - 1 ) {
    str = swap ( str , index , smallGreatDgt ) ;
    return str ;
  }
  return "-1" ;
}

static String prevNum ( String str ) { int len = str . length ( ) ; int index = - 1 ; for ( int i = len - 2 ; i >= 0 ; i -- ) { if ( str . charAt ( i ) > str . charAt ( i + 1 ) ) { index = i ; break ; } } int smallGreatDgt = - 1 ; for ( int i = len - 1 ; i > index ; i -- ) { if ( str . charAt ( i ) < str . charAt ( index ) ) { if ( smallGreatDgt == - 1 ) { smallGreatDgt = i ; } else if ( str . charAt ( i ) >= str . charAt ( smallGreatDgt ) ) { smallGreatDgt = i ; } } } if ( index == - 1 ) { return " - 1" ; } if ( smallGreatDgt != - 1 ) { str = swap ( str , index , smallGreatDgt ) ; return str ; } return " - 1" ; }
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