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extern/stdcxx/4.2.1/examples/manual/nthelem.cpp

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+/**************************************************************************
+ *
+ * nthelem.cpp - Example program for rearranging a collection based on nth
+ *               element.
+ *
+ * $Id: nthelem.cpp 550991 2007-06-26 23:58:07Z sebor $
+ *
+ ***************************************************************************
+ *
+ * Licensed to the Apache Software  Foundation (ASF) under one or more
+ * contributor  license agreements.  See  the NOTICE  file distributed
+ * with  this  work  for  additional information  regarding  copyright
+ * ownership.   The ASF  licenses this  file to  you under  the Apache
+ * License, Version  2.0 (the  "License"); you may  not use  this file
+ * except in  compliance with the License.   You may obtain  a copy of
+ * the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the  License is distributed on an  "AS IS" BASIS,
+ * WITHOUT  WARRANTIES OR CONDITIONS  OF ANY  KIND, either  express or
+ * implied.   See  the License  for  the  specific language  governing
+ * permissions and limitations under the License.
+ *
+ * Copyright 1994-2006 Rogue Wave Software.
+ * 
+ **************************************************************************/
+
+#include <algorithm>   // for swap
+#include <vector>      // for vector
+#include <iostream>    // for cout, endl
+
+#include <examples.h>
+
+
+template <class RandomAccessIterator>
+void quik_sort (RandomAccessIterator beg, RandomAccessIterator end)
+{
+    const long dist = long (end - beg);
+
+    // Stop condition for recursion.
+    if (dist > 2) {
+        // Use nth_element to do all the work for quik_sort.
+        std::nth_element (beg, beg + (dist / 2), end);
+
+        // Recursive calls to each remaining unsorted portion.
+        quik_sort (beg, beg + (dist / 2 - 1));
+        quik_sort (beg + (dist / 2 + 1), end);
+    }
+    else if (2 == dist && *(end - 1) < *beg)
+        std::swap (beg, end);
+}
+
+
+int main ()
+{
+    typedef std::vector<int, std::allocator<int> > Vector;
+
+    // Initialize a vector using an array of integers.
+    const Vector::value_type arr[] = { 37, 12, 2, -5, 14, 1, 0, -1, 14, 32 };
+
+    Vector v (arr, arr + sizeof arr / sizeof *arr);
+
+    // Print the initial vector.
+    std::cout << "The unsorted values are: \n     ";
+
+    for (Vector::iterator i = v.begin (); i != v.end (); ++i)
+        std::cout << *i << ", ";
+
+    std::cout << "\n\n";
+
+    // Use the new sort algorithm.
+    quik_sort (v.begin (), v.end ());
+
+    // Output the sorted vector.
+    std::cout << "The sorted values are: \n     ";
+    for (Vector::iterator j = v.begin (); j != v.end (); ++j)
+        std::cout << *j << ", ";
+
+    std::cout << "\n\n";
+
+    return 0;
+}