libstdc++-v3/testsuite/25_algorithms/nth_element/3.cc

   1 // Copyright (C) 2001 Free Software Foundation, Inc.
   2 //
   3 // This file is part of the GNU ISO C++ Library.  This library is free
   4 // software; you can redistribute it and/or modify it under the
   5 // terms of the GNU General Public License as published by the
   6 // Free Software Foundation; either version 2, or (at your option)
   7 // any later version.
   8
   9 // This library is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13
  14 // You should have received a copy of the GNU General Public License along
  15 // with this library; see the file COPYING.  If not, write to the Free
  16 // Software Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  17 // USA.
  18
  19 // 25.3.1 algorithms, sort()
  20
  21 #include <algorithm>
  22 #include <testsuite_hooks.h>
  23
  24 bool test __attribute__((unused)) = true;
  25
  26 const int A[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20};
  27 const int B[] = {10, 20, 1, 11, 2, 12, 3, 13, 4, 14, 5, 15, 6, 16, 7, 17, 8, 18, 9, 19};
  28 const int C[] = {20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1};
  29 const int N = sizeof(A) / sizeof(int);
  30 const int logN = 3; // ln(N) rounded up
  31 const int P = 7;
  32
  33 // comparison predicate for stable_sort: order by rightmost digit
  34 struct CompLast
  35 {
  36   bool
  37   operator()(const int x, const int y)
  38   { return x % 10 < y % 10; }
  39 };
  40
  41 // This functor has the equivalent functionality of std::geater<>,
  42 // but there is no dependency on <functional> and it also tracks the
  43 // number of invocations since creation.
  44 class Gt
  45 {
  46 public:
  47   static int count() { return itsCount; }
  48   static void reset() { itsCount = 0; }
  49
  50   bool
  51   operator()(const int& x, const int& y)
  52   {
  53     ++itsCount;
  54     return x > y;
  55   }
  56
  57 private:
  58     static int itsCount;
  59 };
  60
  61 int Gt::itsCount = 0;
  62
  63 // 25.3.2 nth_element()
  64 void
  65 test05()
  66 {
  67     using std::nth_element;
  68
  69     int s1[N];
  70     std::copy(B, B + N, s1);
  71     VERIFY(std::equal(s1, s1 + N, B));
  72
  73     int* pn = s1 + (N / 2) - 1;
  74     nth_element(s1, pn, s1 + N);
  75     for (const int* i = pn; i < s1 + N; ++i) VERIFY(!(*i < *pn));
  76
  77     CompLast pred;
  78     nth_element(s1, pn, s1 + N, pred);
  79     for (const int* i = pn; i < s1 + N; ++i) VERIFY(!pred(*i, *pn));
  80 }
  81
  82 int
  83 main()
  84 {
  85   test05();
  86   return 0;
  87 }