refs #338 Topological sorting algorithm, to be used for sorting CLogPattern.

src/blackmisc/algorithm.h

@@ -0,0 +1,79 @@
+/* Copyright (C) 2014
+ * swift project Community / Contributors
+ *
+ * This file is part of swift project. It is subject to the license terms in the LICENSE file found in the top-level
+ * directory of this distribution and at http://www.swift-project.org/license.html. No part of swift project,
+ * including this file, may be copied, modified, propagated, or distributed except according to the terms
+ * contained in the LICENSE file.
+ */
+
+//! \file
+
+#ifndef BLACKMISC_ALGORITHM_H
+#define BLACKMISC_ALGORITHM_H
+
+#include <QtGlobal>
+#include <algorithm>
+#include <iterator>
+
+namespace BlackMisc
+{
+    /*!
+     * Topological sorting algorithm.
+     *
+     * \param begin      Begin iterator of the range to sort.
+     * \param end        End iterator of the range to sort.
+     * \param comparator A binary function which defines a less-than relation between elements of the range.
+     *                   The ordering it induces must be a partial ordering, which is a more relaxed requirement
+     *                   than the strict weak ordering required by most standard sorting algorithms.
+     *
+     * \see https://en.wikipedia.org/wiki/Topological_sorting
+     * \see https://en.wikipedia.org/wiki/Partial_ordering
+     */
+    template <typename I, typename F>
+    void topologicalSort(I begin, I end, F comparator)
+    {
+        using value_type = typename std::iterator_traits<I>::value_type;
+        auto part = begin;
+        while (part != end)
+        {
+            auto newPart = std::partition(part, end, [ = ](const value_type &a)
+            {
+                return std::none_of(part, end, [ =, &a ](const value_type &b)
+                {
+                    return comparator(b, a);
+                });
+            });
+            Q_ASSERT_X(newPart != part, "BlackMisc::topologicalSort", "Cyclic less-than relation detected (not a partial ordering)");
+            part = newPart;
+        }
+    }
+
+    /*!
+     * Insert an element into a sequential container while preserving the topological ordering of the container.
+     *
+     * \param container  A sequential container.
+     * \param value      The value to insert.
+     * \param comparator A binary function which defines a less-than relation between elements of the container.
+     *                   The ordering it induces must be a partial ordering, which is a more relaxed requirement
+     *                   than the strict weak ordering required by most standard sorting algorithms.
+     *
+     * \see https://en.wikipedia.org/wiki/Topological_sorting
+     * \see https://en.wikipedia.org/wiki/Partial_ordering
+     */
+    template <typename C, typename T, typename F>
+    void topologicallySortedInsert(C &container, T &&value, F comparator)
+    {
+        using value_type = typename C::value_type;
+        using reverse = std::reverse_iterator<typename C::iterator>;
+        auto rit = std::find_if(reverse(container.end()), reverse(container.begin()), [ =, &value ](const value_type &lhs)
+        {
+            return comparator(lhs, value);
+        });
+        Q_ASSERT_X(std::none_of(rit, reverse(container.begin()), [ =, &value ](const value_type &rhs) { return comparator(value, rhs); }),
+            "BlackMisc::topologicallySortedInsert", "Cyclic less-than relation detected (not a partial ordering)");
+        container.insert(rit.base(), std::forward<T>(value));
+    }
+}
+
+#endif