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 delete [] array; 46 } 47 48 void 49 test(unsigned N) 50 { 51 test_one(N, 0); 52 test_one(N, 1); 53 test_one(N, 2); 54 test_one(N, 3); 55 test_one(N, N/2-1); 56 test_one(N, N/2); 57 test_one(N, N/2+1); 58 test_one(N, N-3); 59 test_one(N, N-2); 60 test_one(N, N-1); 61 } 62 63 int main() 64 { 65 int d = 0; 66 std::nth_element(&d, &d, &d); 67 assert(d == 0); 68 test(256); 69 test(257); 70 test(499); 71 test(500); 72 test(997); 73 test(1000); 74 test(1009); 75 76 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES 77 { 78 std::vector<std::unique_ptr<int> > v(1000); 79 for (int i = 0; i < v.size(); ++i) 80 v[i].reset(new int(i)); 81 std::nth_element(v.begin(), v.begin() + v.size()/2, v.end(), indirect_less()); 82 assert(*v[v.size()/2] == v.size()/2); 83 } 84 #endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES 85 } 86
