4684ddb6aa
- import libcxx - reduce targets to the one when compiled as a tools Change-Id: Iabb8427f80ff8e89463559a28bcb8b4f2bdbc496
85 lines
2 KiB
C++
85 lines
2 KiB
C++
//===----------------------------------------------------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is dual licensed under the MIT and the University of Illinois Open
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// Source Licenses. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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// <algorithm>
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// template<RandomAccessIterator Iter, StrictWeakOrder<auto, Iter::value_type> Compare>
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// requires ShuffleIterator<Iter>
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// && CopyConstructible<Compare>
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// void
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// nth_element(Iter first, Iter nth, Iter last, Compare comp);
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#include <algorithm>
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#include <functional>
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#include <vector>
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#include <cassert>
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#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
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#include <memory>
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struct indirect_less
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{
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template <class P>
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bool operator()(const P& x, const P& y)
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{return *x < *y;}
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};
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#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
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void
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test_one(unsigned N, unsigned M)
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{
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assert(N != 0);
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assert(M < N);
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int* array = new int[N];
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for (int i = 0; i < N; ++i)
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array[i] = i;
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std::random_shuffle(array, array+N);
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std::nth_element(array, array+M, array+N, std::greater<int>());
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assert(array[M] == N-M-1);
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delete [] array;
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}
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void
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test(unsigned N)
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{
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test_one(N, 0);
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test_one(N, 1);
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test_one(N, 2);
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test_one(N, 3);
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test_one(N, N/2-1);
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test_one(N, N/2);
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test_one(N, N/2+1);
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test_one(N, N-3);
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test_one(N, N-2);
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test_one(N, N-1);
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}
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int main()
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{
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int d = 0;
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std::nth_element(&d, &d, &d);
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assert(d == 0);
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test(256);
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test(257);
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test(499);
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test(500);
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test(997);
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test(1000);
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test(1009);
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#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
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{
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std::vector<std::unique_ptr<int> > v(1000);
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for (int i = 0; i < v.size(); ++i)
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v[i].reset(new int(i));
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std::nth_element(v.begin(), v.begin() + v.size()/2, v.end(), indirect_less());
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assert(*v[v.size()/2] == v.size()/2);
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}
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#endif // _LIBCPP_HAS_NO_RVALUE_REFERENCES
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}
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