C++头文件algorithm 2——Sorting

函数 功能 sort 升序排序 stable_sort 与sort相似，升序排序，但保留元素的相对位置 partial_sort 升序排序部分元素 partial_sort_copy 部分排序并复制已排序的序列 is_sorted 检查是否升序排序 is_sorted_until 找到第一个不满足升序排序的元素 nth_element 仅排序第n个元素，在返回结果中只有第n位元素与最终有序序列的第n位一致

sort

void sort (RandomAccessIterator first, RandomAccessIterator last, Compare comp)
对元素进行排序，默认为升序。first，last表示[first，last)。comp二元函数，为可选参数，设定新的排序规则。

example

#include<iostream>#include<algorithm>#include<vector>using namespace std;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 };    vector<int> myvector(myints, myints + 8);    //using default comparison (operator <)      sort(myvector.begin(),myvector.begin()+4);  //对（32,71,12,45）进行部分升序排序    cout << "default comparison:";    for (vector<int>::iterator it = myvector.begin(); it != myvector.end(); ++it)        cout << *it << " ";    cout << endl;    //using function as comp    sort(myvector.begin() + 4, myvector.end(), myfunction);  //对（26,80,53,33）进行部分升序排序    cout << "function as comp:";    for (vector<int>::iterator it = myvector.begin(); it != myvector.end(); ++it)        cout << *it << " ";    cout << endl;    //using object as comp    sort(myvector.begin(), myvector.end(), myobject); //对全部元素进行升序排序    cout << "object as comp:";    for (vector<int>::iterator it = myvector.begin(); it != myvector.end(); ++it)        cout << *it << " ";    cout << endl;    //using object as comp    return 0;}

output

stable_sort

void stable_sort ( RandomAccessIterator first, RandomAccessIterator last, Compare comp )。stable_sort功能与sort类似，但保持元素之间的相对位置。

example

#include<iostream>#include<algorithm>#include<vector>using namespace std;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 };    vector<double> myvector;    myvector.assign(mydoubles, mydoubles + 8);    cout << "default comparison:";    stable_sort(myvector.begin(), myvector.end());    for (vector<double>::iterator it = myvector.begin(); it != myvector.end(); ++it)        cout << *it << " ";    cout << endl;    myvector.assign(mydoubles, mydoubles + 8);    cout << "compare_as_ints:";    stable_sort(myvector.begin(), myvector.end(), compare_as_ints);    for (vector<double>::iterator it = myvector.begin(); it != myvector.end(); ++it)        cout << *it << " ";    cout << endl;    return 0;}

output

partial_sort

void partial_sort (RandomAccessIterator first, RandomAccessIterator middle, RandomAccessIterator last, Compare comp)
first表示其实位置
middle表示某个中间位置，排序结果中只有从first到middle是有序的
last表示最终位置
comp表示二元函数，自定义的排序规则，可选参数。

example

#include<iostream>#include<algorithm>#include<vector>using namespace std;bool myfunction(int i, int j){ return (i < j); }int main(){    int myints[] = { 9, 8, 7, 6, 5, 4, 3, 2, 1, };    vector<int> myvector(myints, myints + 9);    //using default comparison(operator<)    partial_sort(myvector.begin(), myvector.begin() + 5, myvector.end());    cout << "default comparison:";    for (auto x : myvector)        cout << x << " ";    cout << endl;    //using function as comp    cout << "function as comp:";    partial_sort(myvector.begin(), myvector.begin() + 5, myvector.end());    for (auto x : myvector)        cout << x << " ";    cout << endl;}

output

partial_sort_copy

partial_sort_copy (InputIterator first,InputIterator last, RandomAccessIterator result_first, RandomAccessIterator result_last, Compare comp)

对[first，last)进行排序，并将结果复制保存到[result_first，result_last)。被复制元素的数目是[result_first，result_last)的长度，除非它的长度大于[first，last)中元素数目。comp表示二元函数，自定义的排序规则，可选参数。

example

#include<iostream>#include<algorithm>#include<vector>using namespace std;bool myfunction(int i, int j){ return (i < j); }int main(){    int myints[] = { 9, 8, 7, 6, 5, 4, 3, 2, 1, };    vector<int> myvector(5);    //using default comparison(operator<)    partial_sort_copy(myints, myints + 9, myvector.begin(), myvector.end());    cout << "myvector contains:";    for (auto x : myvector)        cout << x << " ";    cout << endl;    return 0;}

output

is_sorted

bool is_sorted (ForwardIterator first, ForwardIterator last, Compare comp)
first，last表示范围；
comp表示排序规则，二元函数，可选参数。

example

#include<iostream>#include<algorithm>#include<array>using namespace std;int main(){    array<int, 4> myarray = { 2, 3, 1, 4 };    do{        //尝试一个新的排列        prev_permutation(myarray.begin(), myarray.end());        cout << "myarray:";        for (auto x : myarray)            cout << x << " ";        cout << endl;    } while (!is_sorted(myarray.begin(), myarray.end()));    cout << "The array is sorted!" << endl;    return 0;}

output

is_sorted_until

ForwardIterator is_sorted_until (ForwardIterator first, ForwardIterator last, Compare comp)
函数返回在[first，last)中第一个不满足升序排序元素的迭代器。从first到返回的迭代器之间是有序的。如果所有元素是有序的，函数返回last。

example

#include<iostream>#include<algorithm>#include<array>using namespace std;int main(){    array<int, 4> myarray = { 2, 3, 1, 4 };    array<int, 4>::iterator it;    do    {        prev_permutation(myarray.begin(), myarray.end());        cout << "myarray:";        for (auto x : myarray)            cout << x << " ";        it = is_sorted_until(myarray.begin(), myarray.end());        cout << "【" << (it - myarray.begin()) << " elements sorted】\n";    } while (it != myarray.end());    cout << "The array is sorted\n";    return 0;}

output

nth_element

void nth_element (RandomAccessIterator first, RandomAccessIterator nth, RandomAccessIterator last, Compare comp)
first表示起始位置
nth表示要排序的位置
last表示终止位置
comp自定义排序规则，二元函数，可选参数

example

#include<iostream>#include<algorithm>#include<vector>using namespace std;bool myfunction(int i, int j){ return(i < j); }int main(){    vector<int> myvector;    for (int i = 1; i < 10; ++i)        myvector.push_back(i);    random_shuffle(myvector.begin(), myvector.end());    cout << "myvector contains:";    for (auto x : myvector)        cout << x << " ";    cout << endl;    nth_element(myvector.begin(), myvector.begin() + 5, myvector.end());    cout << "default comparison:";    for (auto x : myvector)        cout << x << " ";    cout << endl;    random_shuffle(myvector.begin(), myvector.end());    cout << "myvector contains:";    for (auto x : myvector)        cout << x << " ";    cout << endl;    nth_element(myvector.begin(),myvector.begin()+5, myvector.end(), myfunction);    cout << "function as comp:";    for (auto x : myvector)        cout << x << " ";    cout << endl;    return 0;}

output