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Telegram/ThirdParty/range-v3/test/algorithm/nth_element.cpp

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+// Range v3 library
+//
+//  Copyright Eric Niebler 2014-present
+//
+//  Use, modification and distribution is subject to the
+//  Boost Software License, Version 1.0. (See accompanying
+//  file LICENSE_1_0.txt or copy at
+//  http://www.boost.org/LICENSE_1_0.txt)
+//
+// Project home: https://github.com/ericniebler/range-v3
+
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include <memory>
+#include <random>
+#include <algorithm>
+#include <range/v3/core.hpp>
+#include <range/v3/algorithm/nth_element.hpp>
+#include "../simple_test.hpp"
+#include "../test_utils.hpp"
+#include "../test_iterators.hpp"
+
+RANGES_DIAGNOSTIC_IGNORE_GLOBAL_CONSTRUCTORS
+RANGES_DIAGNOSTIC_IGNORE_SIGN_CONVERSION
+
+namespace
+{
+    std::mt19937 gen;
+
+    void
+    test_one(unsigned N, unsigned M)
+    {
+        RANGES_ENSURE(N != 0);
+        RANGES_ENSURE(M < N);
+        std::unique_ptr<int[]> array{new int[N]};
+        for (int i = 0; (unsigned)i < N; ++i)
+            array[i] = i;
+        std::shuffle(array.get(), array.get()+N, gen);
+        CHECK(ranges::nth_element(array.get(), array.get()+M, array.get()+N) == array.get()+N);
+        CHECK((unsigned)array[M] == M);
+        std::shuffle(array.get(), array.get()+N, gen);
+        CHECK(ranges::nth_element(::as_lvalue(ranges::make_subrange(array.get(), array.get()+N)), array.get()+M) == array.get()+N);
+        CHECK((unsigned)array[M] == M);
+        std::shuffle(array.get(), array.get()+N, gen);
+        CHECK(ranges::nth_element(ranges::make_subrange(array.get(), array.get()+N), array.get()+M) == array.get()+N);
+        CHECK((unsigned)array[M] == M);
+        ranges::nth_element(array.get(), array.get()+N, array.get()+N); // first, last, end
+    }
+
+    void
+    test(unsigned N)
+    {
+        test_one(N, 0);
+        test_one(N, 1);
+        test_one(N, 2);
+        test_one(N, 3);
+        test_one(N, N/2-1);
+        test_one(N, N/2);
+        test_one(N, N/2+1);
+        test_one(N, N-3);
+        test_one(N, N-2);
+        test_one(N, N-1);
+    }
+
+    struct S
+    {
+        int i,j;
+    };
+}
+
+int main()
+{
+    int d = 0;
+    ranges::nth_element(&d, &d, &d);
+    CHECK(d == 0);
+    test(256);
+    test(257);
+    test(499);
+    test(500);
+    test(997);
+    test(1000);
+    test(1009);
+
+    // Works with projections?
+    const int N = 257;
+    const int M = 56;
+    S ia[N];
+    for(int i = 0; i < N; ++i)
+        ia[i].i = ia[i].j = i;
+    std::shuffle(ia, ia+N, gen);
+    ranges::nth_element(ia, ia+M, std::less<int>(), &S::i);
+    CHECK(ia[M].i == M);
+    CHECK(ia[M].j == M);
+
+    return test_result();
+}