static int CountContiguousParts ( int arr [ ] , int n ) {
  int count = 0 ;
  int [ ] prefix = new int [ n ] ;
  prefix [ 0 ] = arr [ 0 ] ;
  for ( int i = 1 ;
  i < n ;
  i ++ ) prefix [ i ] = prefix [ i - 1 ] + arr [ i ] ;
  int total_sum = prefix [ n - 1 ] ;
  if ( total_sum % 3 != 0 ) return 0 ;
  int [ ] suffix = new int [ n ] ;
  suffix [ n - 1 ] = arr [ n - 1 ] ;
  for ( int i = n - 2 ;
  i >= 0 ;
  i -- ) suffix [ i ] = suffix [ i + 1 ] + arr [ i ] ;
  Vector < Integer > v = new Vector < > ( ) ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) if ( suffix [ i ] == total_sum / 3 ) v . add ( i ) ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    if ( prefix [ i ] == total_sum / 3 ) {
      int res = binarysearch ( v , i + 1 ) ;
      if ( res != - 1 ) count += v . size ( ) - res ;
    }
  }
  return count ;
}

static int CountContiguousParts ( int arr [ ] , int n ) { int count = 0 ; int [ ] prefix = new int [ n ] ; prefix [ 0 ] = arr [ 0 ] ; for ( int i = 1 ; i < n ; i ++ ) prefix [ i ] = prefix [ i - 1 ] + arr [ i ] ; int total_sum = prefix [ n - 1 ] ; if ( total_sum % 3 != 0 ) return 0 ; int [ ] suffix = new int [ n ] ; suffix [ n - 1 ] = arr [ n - 1 ] ; for ( int i = n - 2 ; i >= 0 ; i -- ) suffix [ i ] = suffix [ i + 1 ] + arr [ i ] ; Vector < Integer > v = new Vector < > ( ) ; for ( int i = 0 ; i < n ; i ++ ) if ( suffix [ i ] == total_sum / 3 ) v . add ( i ) ; for ( int i = 0 ; i < n ; i ++ ) { if ( prefix [ i ] == total_sum / 3 ) { int res = binarysearch ( v , i + 1 ) ; if ( res != - 1 ) count += v . size ( ) - res ; } } return count ; }
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