static int lenghtOfLongestAP ( int set [ ] , int n ) {
  if ( n <= 2 ) return n ;
  int L [ ] [ ] = new int [ n ] [ n ] ;
  int llap = 2 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) L [ i ] [ n - 1 ] = 2 ;
  for ( int j = n - 2 ;
  j >= 1 ;
  j -- ) {
    int i = j - 1 , k = j + 1 ;
    while ( i >= 0 && k <= n - 1 ) {
      if ( set [ i ] + set [ k ] < 2 * set [ j ] ) k ++ ;
      else if ( set [ i ] + set [ k ] > 2 * set [ j ] ) {
        L [ i ] [ j ] = 2 ;
        i -- ;
      }
      else {
        L [ i ] [ j ] = L [ j ] [ k ] + 1 ;
        llap = Math . max ( llap , L [ i ] [ j ] ) ;
        i -- ;
        k ++ ;
      }
    }
    while ( i >= 0 ) {
      L [ i ] [ j ] = 2 ;
      i -- ;
    }
  }
  return llap ;
}

static int lenghtOfLongestAP ( int set [ ] , int n ) { if ( n <= 2 ) return n ; int L [ ] [ ] = new int [ n ] [ n ] ; int llap = 2 ; for ( int i = 0 ; i < n ; i ++ ) L [ i ] [ n - 1 ] = 2 ; for ( int j = n - 2 ; j >= 1 ; j -- ) { int i = j - 1 , k = j + 1 ; while ( i >= 0 && k <= n - 1 ) { if ( set [ i ] + set [ k ] < 2 * set [ j ] ) k ++ ; else if ( set [ i ] + set [ k ] > 2 * set [ j ] ) { L [ i ] [ j ] = 2 ; i -- ; } else { L [ i ] [ j ] = L [ j ] [ k ] + 1 ; llap = Math . max ( llap , L [ i ] [ j ] ) ; i -- ; k ++ ; } } while ( i >= 0 ) { L [ i ] [ j ] = 2 ; i -- ; } } return llap ; }
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