public static int countKdivPairs ( int A [ ] , int n , int K ) {
  int freq [ ] = new int [ K ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) ++ freq [ A [ i ] % K ] ;
  int sum = freq [ 0 ] * ( freq [ 0 ] - 1 ) / 2 ;
  for ( int i = 1 ;
  i <= K / 2 && i != ( K - i ) ;
  i ++ ) sum += freq [ i ] * freq [ K - i ] ;
  if ( K % 2 == 0 ) sum += ( freq [ K / 2 ] * ( freq [ K / 2 ] - 1 ) / 2 ) ;
  return sum ;
}

public static int countKdivPairs ( int A [ ] , int n , int K ) { int freq [ ] = new int [ K ] ; for ( int i = 0 ; i < n ; i ++ ) ++ freq [ A [ i ] % K ] ; int sum = freq [ 0 ] * ( freq [ 0 ] - 1 ) / 2 ; for ( int i = 1 ; i <= K / 2 && i != ( K - i ) ; i ++ ) sum += freq [ i ] * freq [ K - i ] ; if ( K % 2 == 0 ) sum += ( freq [ K / 2 ] * ( freq [ K / 2 ] - 1 ) / 2 ) ; return sum ; }
(method_declaration (modifiers) type: (integral_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (integral_type) name: (identifier) dimensions: (dimensions)) (formal_parameter type: (integral_type) name: (identifier)) (formal_parameter type: (integral_type) name: (identifier))) body: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) dimensions: (dimensions) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (identifier))))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (identifier)) update: (update_expression (identifier)) body: (expression_statement (update_expression (array_access array: (identifier) index: (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (identifier)))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (binary_expression left: (array_access array: (identifier) index: (decimal_integer_literal)) right: (parenthesized_expression (binary_expression left: (array_access array: (identifier) index: (decimal_integer_literal)) right: (decimal_integer_literal)))) right: (decimal_integer_literal)))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (binary_expression left: (identifier) right: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (binary_expression left: (identifier) right: (parenthesized_expression (binary_expression left: (identifier) right: (identifier))))) update: (update_expression (identifier)) body: (expression_statement (assignment_expression left: (identifier) right: (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (identifier))))))) (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (identifier) right: (decimal_integer_literal)) right: (decimal_integer_literal))) consequence: (expression_statement (assignment_expression left: (identifier) right: (parenthesized_expression (binary_expression left: (binary_expression left: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (parenthesized_expression (binary_expression left: (array_access array: (identifier) index: (binary_expression left: (identifier) right: (decimal_integer_literal))) right: (decimal_integer_literal)))) right: (decimal_integer_literal)))))) (return_statement (identifier))))