C++ sort(),stable_sort()和partial_sort()

写了那么多的排序，但是其实C++里封装有排序函数，而且功能非常强大。

sort函数有sort(),stable_sort()和partial_sort()。sort()函数是对给定区间的元素进行排序，stable_sort()是对给定区间的元素进行稳定排序，如果两个元素相等，那么排序完成后两个元素的相对位置保持不变，partial_sort()是对给定区间的元素进行部分排序。默认的顺序是由小到大进行排序。

下面是三个函数的使用示例：

1 sort()

#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;
}

2 stable_sort()

#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;
}

3 partial_sort()

#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;
}