STL之排序算法

Sorting

sort	Sort elements in range (function template)
stable_sort	Sort elements preserving order of equivalents (function template )
partial_sort	Partially Sort elements in range (function template)
partial_sort_copy	Copy and partially sort range (function template)
nth_element	Sort element in range (function template)

其中sort,和stable_sort在我的多篇博客出现过，在此不再累赘，想复习sort和stable_sort的朋友，可以翻看我的博客

1partial_sort

template <class RandomAccessIterator>
  void partial_sort ( RandomAccessIterator first, RandomAccessIterator middle,
                      RandomAccessIterator last );

template <class RandomAccessIterator, class Compare>
  void partial_sort ( RandomAccessIterator first, RandomAccessIterator middle,
                      RandomAccessIterator last, Compare comp );

以上是它的函数原型，它是根据你给的中间地址，然后部分排序，比如你给的地址是 v.begin(),v.begin()+5,v.end()，其中v的大小是10那么结果就是前面五个排序了，后面五个按照原来的顺序，看代码

#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<functional>
using namespace std;
int main(){
	int a[]={10,9,8,7,6,5,4,3,2,1};
	vector<int>v(a,a+10);
	partial_sort(v.begin(),v.begin()+5,v.end());
	for(vector<int>::iterator itera=v.begin();itera!=v.end();++itera){
		cout<<*itera<<" ";
	}
	cout<<endl;
	system("pause");
	return 0;
}

#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<functional>
using namespace std;
bool isBigger(int a,int b){
	return a>b;
}
int main(){
	int a[]={1,2,3,4,5,6,7,8,9,10};
	vector<int>v(a,a+10);
	partial_sort(v.begin(),v.begin()+5,v.end(),isBigger);
	for(vector<int>::iterator itera=v.begin();itera!=v.end();++itera){
		cout<<*itera<<" ";
	}
	cout<<endl;
	system("pause");
	return 0;
}

代码简单，不必解释了吧。

2partial_sort_copy,

函数原型如下：

template <class InputIterator, class RandomAccessIterator>
  RandomAccessIterator
    partial_sort_copy ( InputIterator first,InputIterator last,
                        RandomAccessIterator result_first,
                        RandomAccessIterator result_last );

template <class InputIterator, class RandomAccessIterator, class Compare>
  RandomAccessIterator
    partial_sort_copy ( InputIterator first,InputIterator last,
                        RandomAccessIterator result_first,
                        RandomAccessIterator result_last, Compare comp );

其实它就相当于sort()和copy的结合，所谓的partial没有给定范围，实际上用的比较多的，还是begin--->end

看代码：

#include<iostream>
#include<string>
#include<algorithm>
#include<functional>
#include<vector>
using namespace std;
int main(){
	int a[]={4,5,2,1,3,6,9,8,7,2};
	vector<int>v(a,a+10);
	vector<int>vv(10);
	partial_sort_copy(v.begin(),v.end(),vv.begin(),vv.end());
	for(vector<int>::iterator itera=vv.begin(); itera!=vv.end();++itera){
		cout<<*itera<<" ";
	}
	cout<<endl;
	system("pause");
	return 0;
}

#include<iostream>
#include<string>
#include<algorithm>
#include<functional>
#include<vector>
using namespace std;
bool isBigger(int a,int b){
	return a>b;
}
int main(){
	int a[]={4,5,2,1,3,6,9,8,7,2};
	vector<int>v(a,a+10);
	vector<int>vv(10);
	partial_sort_copy(v.begin(),v.end(),vv.begin(),vv.end(),isBigger);
	for(vector<int>::iterator itera=vv.begin(); itera!=vv.end();++itera){
		cout<<*itera<<" ";
	}
	cout<<endl;
	system("pause");
	return 0;
}

3nth_element,STL中的nth_element()方法的使用通过调用nth_element(start, start+n, end) 方法可以使第n大元素处于第n位置（从0开始,其位置是下标为 n的元素），并且比这个元素小的元素都排在这个元素之前，比这个元素大的元素都排在这个元素之后，但不能保证他们是有序的

其函数原型如下：

template <class RandomAccessIterator>
  void nth_element ( RandomAccessIterator first, RandomAccessIterator nth,
                     RandomAccessIterator last );

template <class RandomAccessIterator, class Compare>
  void nth_element ( RandomAccessIterator first, RandomAccessIterator nth,
                     RandomAccessIterator last, Compare comp );

看下代码：

#include<iostream>
#include<string>
#include<vector>
#include<algorithm>
#include<functional>
using namespace std;
int main(){
	int a[]={10,4,2,7,6,5,9,3,8,1};
	vector<int>v(a,a+10);
	for(vector<int>::iterator itera=v.begin();itera!=v.end();++itera){
		cout<<*itera<<" ";
	}
	cout<<endl;
	nth_element(v.begin(),v.begin()+6,v.end());
	for(vector<int>::iterator iterb=v.begin();iterb!=v.end();++iterb){
		cout<<*iterb<<" ";
	}
	cout<<endl;
	system("pause");
	return 0;
}