使用sort算法对vector进行排序(对vector<string>排序、使用稳定的排序std::stable_sort())
最后更新于：2022-04-01 06:44:28
##实战c++中的vector系列--使用sort算法对vector进行排序(对vector<string>排序、使用稳定的排序std::stable_sort())
写了挺多关于vector的操作了，正好工作中遇到对vector进行排序的问题，这里就讨论一下。
直接使用sort算法，那就先了解一下：
~~~
template <class RandomAccessIterator>
void sort (RandomAccessIterator first, RandomAccessIterator last);
template <class RandomAccessIterator, class Compare>
void sort (RandomAccessIterator first, RandomAccessIterator last, Compare comp);
~~~
Sorts the elements in the range [first,last) into ascending order.
The elements are compared using operator< for the first version, and comp for the second.
Equivalent elements are not guaranteed to keep their original relative order (see stable_sort).
也就是所说的不稳定排序。
直接上代码：
~~~
#include <iostream> // std::cout
#include <algorithm> // std::sort
#include <vector> // std::vector
#include <string>
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';
// Sorting the string vector
std::vector<std::string> stringVec = { "John", "Bob", "Joe", "Zack", "Randy" };
sort(stringVec.begin(), stringVec.end());
for (std::string &s : stringVec)
std::cout << s << " ";
return 0;
}
//输出：
myvector contains: 12 26 32 33 45 53 71 80
Bob Joe John Randy Zack
~~~
这个时候可以使用std::stable_sort()来实现稳定的排序了：
Sorts the elements in the range [first,last) into ascending order, like sort, but stable_sort preserves the relative order of the elements with equivalent values.
~~~
#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：
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
~~~