1 //===----------------------------------------------------------------------===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is dual licensed under the MIT and the University of Illinois Open 6 // Source Licenses. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 // <algorithm> 11 12 // template<RandomAccessIterator Iter, StrictWeakOrder<auto, Iter::value_type> Compare> 13 // requires ShuffleIterator<Iter> 14 // && CopyConstructible<Compare> 15 // void 16 // nth_element(Iter first, Iter nth, Iter last, Compare comp); 17 18 #include <algorithm> 19 #include <functional> 20 #include <vector> 21 #include <cassert> 22 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES 23 #include <memory> 24 25 struct indirect_less 26 { 27 template <class P> 28 bool operator()(const P& x, const P& y) 29 {return *x < *y;} 30 }; 31 32 #endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES 33 34 void 35 test_one(unsigned N, unsigned M) 36 { 37 assert(N != 0); 38 assert(M < N); 39 int* array = new int[N]; 40 for (int i = 0; i < N; ++i) 41 array[i] = i; 42 std::random_shuffle(array, array+N); 43 std::nth_element(array, array+M, array+N, std::greater<int>()); 44 assert(array[M] == N-M-1); 45 std::nth_element(array, array+N, array+N, std::greater<int>()); // begin, end, end 46 delete [] array; 47 } 48 49 void 50 test(unsigned N) 51 { 52 test_one(N, 0); 53 test_one(N, 1); 54 test_one(N, 2); 55 test_one(N, 3); 56 test_one(N, N/2-1); 57 test_one(N, N/2); 58 test_one(N, N/2+1); 59 test_one(N, N-3); 60 test_one(N, N-2); 61 test_one(N, N-1); 62 } 63 64 int main() 65 { 66 int d = 0; 67 std::nth_element(&d, &d, &d); 68 assert(d == 0); 69 test(256); 70 test(257); 71 test(499); 72 test(500); 73 test(997); 74 test(1000); 75 test(1009); 76 77 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES 78 { 79 std::vector<std::unique_ptr<int> > v(1000); 80 for (int i = 0; i < v.size(); ++i) 81 v[i].reset(new int(i)); 82 std::nth_element(v.begin(), v.begin() + v.size()/2, v.end(), indirect_less()); 83 assert(*v[v.size()/2] == v.size()/2); 84 } 85 #endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES 86 } 87