c++中的sort 排序函数 less和greater使用

http://www.cplusplus.com/reference/functional/less/ http://www.cplusplus.com/reference/algorithm/sort/?kw=sort

c++中的sort 排序函数

默认排序，从小到大 template <class RandomAccessIterator> void sort (RandomAccessIterator first, RandomAccessIterator last); 通过第三个参数来执行排序（从小到大或者从大到小） template <class RandomAccessIterator, class Compare> void sort (RandomAccessIterator first, RandomAccessIterator last, Compare comp); // 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> my_vector (myints, myints+8); // 32 71 12 45 26 80 53 33 // using default comparison (operator <): std::sort (my_vector.begin(), my_vector.begin()+4); //(12 32 45 71)26 80 53 33 // using function as comp std::sort (my_vector.begin()+4, my_vector.end(), myfunction); // 12 32 45 71(26 33 53 80) // using object as comp std::sort (my_vector.begin(), my_vector.end(), myobject); //(12 26 32 33 45 53 71 80) // print out content: std::cout << "my_vector contains:"; for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it) std::cout << ' ' << *it; std::cout << '\n'; return 0; } my_vector contains: 12 26 32 33 45 53 71 80

另外，c++中提供了比较函数，就不需要我们来重新写比较函数了

less<type>() //从小到大排序 < grater<type>() //从大到小排序 > less_equal<type>() // <= gtater_equal<type>()// >= //这四种函数 // greater example #include <iostream> // std::cout #include <functional> // std::greater #include <algorithm> // std::sort int main () { int numbers[]={20,40,50,10,30}; std::sort (numbers, numbers+5, std::greater<int>()); for (int i=0; i<5; i++) std::cout << numbers[i] << ' '; std::cout << '\n'; return 0; }

set集合默认排序方式 从小到大即less的，我们可以通过创建set的时候指定排序方式

set<int,greater<int>> m_set = { 1, 1, 5, 3, 2, 9, 6, 7, 7 }; for each (auto var in m_set) { cout << var << " "; }

另外如果闲创建的比较繁琐我们可以用typedef来重命名

typedef std::set<int,std::greater<int>> IntSet; typedef std::set<int,std::less<int>> IntSet; IntSet my_set IntSet::iterator ipos;