C++ 算法库(4) 排序操作

排序操作：

is_sorted C++11	检测指定范围是否已排序
is_sorted_until C++11	返回最大已排序子范围
nth_element	部份排序指定范围中的元素，使得范围按给定位置处的元素划分
partial_sort	部份排序
partial_sort_copy	拷贝部分排序的结果
sort	排序
stable_sort	稳定排序

is_sorted

检测指定范围是否已排序

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// is_sorted example #include <iostream> // std::cout #include <algorithm> // std::is_sorted, std::prev_permutation #include <array> // std::array int main () { std::array<int,4> foo {2,4,1,3}; do { // try a new permutation: std::prev_permutation(foo.begin(),foo.end()); // print range: std::cout << "foo:"; for (int& x:foo) std::cout << ' ' << x; std::cout << '\n'; } while (!std::is_sorted(foo.begin(),foo.end())); std::cout << "the range is sorted!\n"; return 0; }

输出：

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foo: 2 3 4 1 foo: 2 3 1 4 foo: 2 1 4 3 foo: 2 1 3 4 foo: 1 4 3 2 foo: 1 4 2 3 foo: 1 3 4 2 foo: 1 3 2 4 foo: 1 2 4 3 foo: 1 2 3 4 the range is sorted!

is_sorted_until

返回最大已排序子范围

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// is_sorted_until example #include <iostream> // std::cout #include <algorithm> // std::is_sorted_until, std::prev_permutation #include <array> // std::array int main () { std::array<int,4> foo {2,4,1,3}; std::array<int,4>::iterator it; do { // try a new permutation: std::prev_permutation(foo.begin(),foo.end()); // print range: std::cout << "foo:"; for (int& x:foo) std::cout << ' ' << x; it=std::is_sorted_until(foo.begin(),foo.end()); std::cout << " (" << (it-foo.begin()) << " elements sorted)\n"; } while (it!=foo.end()); std::cout << "the range is sorted!\n"; return 0; }

输出：

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foo: 2 3 4 1 (3 elements sorted) foo: 2 3 1 4 (2 elements sorted) foo: 2 1 4 3 (1 elements sorted) foo: 2 1 3 4 (1 elements sorted) foo: 1 4 3 2 (2 elements sorted) foo: 1 4 2 3 (2 elements sorted) foo: 1 3 4 2 (3 elements sorted) foo: 1 3 2 4 (2 elements sorted) foo: 1 2 4 3 (3 elements sorted) foo: 1 2 3 4 (4 elements sorted) the range is sorted!

nth_element

部份排序指定范围中的元素，使得范围按给定位置处的元素划分

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// nth_element example #include <iostream> // std::cout #include <algorithm> // std::nth_element, std::random_shuffle #include <vector> // std::vector bool myfunction (int i,int j) { return (i<j); } int main () { std::vector<int> myvector; // set some values: for (int i=1; i<10; i++) myvector.push_back(i); // 1 2 3 4 5 6 7 8 9 std::random_shuffle (myvector.begin(), myvector.end()); // using default comparison (operator <): std::nth_element (myvector.begin(), myvector.begin()+5, myvector.end()); // using function as comp std::nth_element (myvector.begin(), myvector.begin()+5, myvector.end(),myfunction); // print out content: std::cout << "myvector contains:"; for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it) std::cout << ' ' << *it; std::cout << '\n'; return 0; }

输出：

1

myvector contains: 3 1 4 2 5 6 9 7 8

partial_sort

部份排序

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// partial_sort example #include <iostream> // std::cout #include <algorithm> // std::partial_sort #include <vector> // std::vector bool myfunction (int i,int j) { return (i<j); } int main () { int myints[] = {9,8,7,6,5,4,3,2,1}; std::vector<int> myvector (myints, myints+9); // using default comparison (operator <): std::partial_sort (myvector.begin(), myvector.begin()+5, myvector.end()); // using function as comp std::partial_sort (myvector.begin(), myvector.begin()+5, myvector.end(),myfunction); // print out content: std::cout << "myvector contains:"; for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it) std::cout << ' ' << *it; std::cout << '\n'; return 0; }

输出：

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myvector contains: 1 2 3 4 5 9 8 7 6

partial_sort_copy

拷贝部分排序的结果

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// partial_sort_copy example #include <iostream> // std::cout #include <algorithm> // std::partial_sort_copy #include <vector> // std::vector bool myfunction (int i,int j) { return (i<j); } int main () { int myints[] = {9,8,7,6,5,4,3,2,1}; std::vector<int> myvector (5); // using default comparison (operator <): std::partial_sort_copy (myints, myints+9, myvector.begin(), myvector.end()); // using function as comp std::partial_sort_copy (myints, myints+9, myvector.begin(), myvector.end(), myfunction); // print out content: std::cout << "myvector contains:"; for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it) std::cout << ' ' << *it; std::cout << '\n'; return 0; }

输出：

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myvector contains: 1 2 3 4 5

sort

排序

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// sort algorithm example #include <iostream> // std::cout #include <algorithm> // std::sort #include <vector> // std::vector bool myfunction (int i,int j) { return (i<j); } struct myclass { bool operator() (int i,int j) { return (i<j);} } myobject; int main () { int myints[] = {32,71,12,45,26,80,53,33}; std::vector<int> myvector (myints, myints+8); // 32 71 12 45 26 80 53 33 // using default comparison (operator <): std::sort (myvector.begin(), myvector.begin()+4); //(12 32 45 71)26 80 53 33 // using function as comp std::sort (myvector.begin()+4, myvector.end(), myfunction); // 12 32 45 71(26 33 53 80) // using object as comp std::sort (myvector.begin(), myvector.end(), myobject); //(12 26 32 33 45 53 71 80) // print out content: std::cout << "myvector contains:"; for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it) std::cout << ' ' << *it; std::cout << '\n'; return 0; }

输出：

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myvector contains: 12 26 32 33 45 53 71 80

stable_sort

稳定排序

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// stable_sort example #include <iostream> // std::cout #include <algorithm> // std::stable_sort #include <vector> // std::vector bool compare_as_ints (double i,double j) { return (int(i)<int(j)); } int main () { double mydoubles[] = {3.14, 1.41, 2.72, 4.67, 1.73, 1.32, 1.62, 2.58}; std::vector<double> myvector; myvector.assign(mydoubles,mydoubles+8); std::cout << "using default comparison:"; std::stable_sort (myvector.begin(), myvector.end()); for (std::vector<double>::iterator it=myvector.begin(); it!=myvector.end(); ++it) std::cout << ' ' << *it; std::cout << '\n'; myvector.assign(mydoubles,mydoubles+8); std::cout << "using 'compare_as_ints' :"; std::stable_sort (myvector.begin(), myvector.end(), compare_as_ints); for (std::vector<double>::iterator it=myvector.begin(); it!=myvector.end(); ++it) std::cout << ' ' << *it; std::cout << '\n'; return 0; }

输出：

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using default comparison: 1.32 1.41 1.62 1.73 2.58 2.72 3.14 4.67 using 'compare_as_ints' : 1.41 1.73 1.32 1.62 2.72 2.58 3.14 4.67

特别说明：函数的中文释义来自：http://classfoo.cn/cpp/head/76573_319/，例子来自：http://www.cplusplus.com/reference/algorithm/