极客笔记C++ 算法 sort()函数
C++ 算法 sort() 函数用于将区间[first, last)中的元素按升序排序。
元素的比较使用运算符 < 进行，对于第二个版本，使用 comp 进行比较。
语法
default (1)
template <class RandomAccessIterator>
void sort (RandomAccessIterator first, RandomAccessIterator last);
custom (2)
template <class RandomAccessIterator, class Compare>
void sort (RandomAccessIterator first, RandomAccessIterator last, Compare comp);
参数
first ：一个随机访问迭代器，指向要排序范围中的第一个元素。
last ：一个随机访问迭代器，指向要排序范围中的最后一个元素的下一个位置。
comp ：一个用户定义的二元谓词函数，接受两个参数，并在这两个参数有序时返回true，否则返回false。它遵循严格弱排序规则来排序元素。
返回值
无
复杂度
排序复杂度的平均值为N*log 2 (N)，其中N = last – first。
数据竞争
范围[first, last)内的对象将被修改。
异常
如果元素比较、元素交换或迭代器操作中的任何一个引发异常，此函数将抛出异常。
注意：无效参数将导致未定义行为。
示例1
让我们看一个简单的示例来演示sort()的使用：
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
int main()
{
vector<int> v = {3, 1, 4, 2, 5};
cout<<"Before sorting: ";
for_each(v.begin(), v.end(), [](int x) {
cout << x << " ";
});
sort(v.begin(), v.end());
cout<<"\nAfter sorting: ";
for_each(v.begin(), v.end(), [](int x) {
cout << x << " ";
});
return 0;
}
输出:
Before sorting: 3 1 4 2 5
After sorting: 1 2 3 4 5
示例2
让我们看看另一个简单的示例：
#include <iostream> // std::cout
#include <algorithm> // std::sort
#include <vector> // std::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); // 32 71 12 45 26 80 53 33
// using default comparison (operator <):
sort (myvector.begin(), myvector.begin()+4); //(12 32 45 71)26 80 53 33
// using function as comp
sort (myvector.begin()+4, myvector.end(), myfunction); // 12 32 45 71(26 33 53 80)
// using object as comp
sort (myvector.begin(), myvector.end(), myobject); //(12 26 32 33 45 53 71 80)
// print out content:
cout << "myvector contains:";
for (vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
cout << ' ' << *it;
cout << '\n';
return 0;
}
输出：
myvector contains: 12 26 32 33 45 53 71 80
示例3
让我们看一个简单的示例：
#include <iostream>
#include <vector>
#include <algorithm>
#include <functional>
using namespace std;
void print(const vector <std::string>& v)
{
vector <string>::const_iterator i;
for(i = v.begin(); i != v.end(); i++)
{
cout << *i << " ";
}
cout << endl;
}
int main()
{
vector <string> v;
// Push functional programming languages
v.push_back("Lisp");
v.push_back("C#");
v.push_back("Java");
v.push_back("Python");
v.push_back("C++");
v.push_back("Pascal");
v.push_back("Sql");
// sort without predicate
sort(v.begin(), v.end());
cout << "Sorted list of functional programming languages - " << endl;
print(v);
// sort with predicate
sort(v.begin(), v.end(), std::greater<std::string>());
cout << "Reverse Sorted list of functional programming languages - " << endl;
print(v);
}
输出：
Sorted list of functional programming languages -
C# C++ Java Lisp Pascal Python Sql
Reverse Sorted list of functional programming languages -
Sql Python Pascal Lisp Java C++ C#
示例4
让我们看另一个简单的示例：
#include <vector>
#include <algorithm>
#include <functional>
#include <iostream>
using namespace std;
// return whether first element is greater than the second
bool userdefgreater(int elem1, int elem2)
{ return elem1 > elem2; }
int main()
{
vector <int> vec1; // container
vector <int>::iterator Iter1; // iterator
int k;
for (k = 0; k <= 15; k++)
vec1.push_back(k);
random_shuffle(vec1.begin(), vec1.end());
cout <<"Original random shuffle vector vec1 data:\n";
for (Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)
cout <<*Iter1<<" ";
cout <<endl;
sort(vec1.begin(), vec1.end());
cout <<"\nSorted vector vec1 data:\n";
for (Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)
cout <<*Iter1<<" ";
cout <<endl;
// to sort in descending order, specify binary predicate
sort(vec1.begin(), vec1.end(), greater<int>());
cout <<"\nRe sorted (greater) vector vec1 data:\n";
for (Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)
cout <<*Iter1<<" ";
cout <<endl;
// a user-defined binary predicate can also be used
sort(vec1.begin(), vec1.end(), userdefgreater);
cout <<"\nUser defined re sorted vector vec1 data:\n";
for (Iter1 = vec1.begin(); Iter1 != vec1.end(); Iter1++)
cout <<*Iter1<<" ";
cout <<endl;
return 0;
}
输出：
Original random shuffle vector vec1 data:
4 10 11 15 14 5 13 1 6 9 3 7 8 2 0 12
Sorted vector vec1 data:
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Re sorted (greater) vector vec1 data:
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
User defined re sorted vector vec1 data:
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0