Detailed Explanation of STL Standard Library Sorting Algorithm (Part 1)

        This blog is after I took a break and found that I haven’t used handwriting for several days. Hahaha, so I may update frequently for a period of time recently. The blogs these days are full of dry goods!

Hehe, Xiaohou should wake up and write something he understands, so as to enhance his knowledge reserve.

Okay, let’s get into the text. The sorting algorithm has a lot of content, so we use separate codes to explain it. Please read the content in the code section carefully for a detailed explanation of the sorting function.

code show as below:

#include<iostream>
#include<vector>
#include<list> 
#include<algorithm>
using namespace std;
/*
	这篇博客主讲STL中四大算法中的排序算法
	排序算法的特点是对容器的内容进行不同方式的排序
	例如sort（） 
*/

void output(int val)
{
	cout << val << " ";
}
int main()
{
	vector<int> ivc1,ivc2;
	int n1,n2,x;
	cout << "请输入ivc1的容器大小：" << endl;
	cin >> n1;
	for(int i = 0; i < n1; i++)
	{
		cin >> x;
		ivc1.push_back(x);
	}
	cout << "请输入ivc2的容器大小：" << endl;
	cin >> n2;
	for(int i = 0; i < n2; i++)
	{
		cin >> x;
		ivc2.push_back(x);
	}
//	ivc2.resize(n);
//	copy(ivc1.begin(),ivc1.end(),ivc2.begin());
	cout << "ivc1 :" << endl;
	for_each(ivc1.begin(),ivc1.end(),output);
	cout << endl;
	cout << "ivc2 :" << endl;
	for_each(ivc2.begin(),ivc2.end(),output);
	cout << endl <<endl;
	
	/*
		binary_search(first,last,val) 二分法寻找 
		first,last是指向容器的迭代器
		val是要寻找的元素
		找到的话返回值为1，否则返回值为0 
	*/
	cout << "After binary_search():" << endl;
	if(binary_search(ivc1.begin(),ivc1.end(),5))
		cout << "Found(5)!" << endl;
	else 
		cout << "Not found(5)!" << endl;
	cout << endl;
	
	/*
		equal_range(first,last,val)
		返回两个迭代器即区间，val是要查询的值
		区间使用pair（）可以包含两个多种类型的数据 
	*/ 
	cout << "After equal_range():" << endl;
	pair<vector<int>::iterator,vector<int>::iterator> it;
	it = equal_range(ivc1.begin(),ivc1.end(),7);
	cout << *it.first << " " << *it.second;
	cout << endl <<endl;
	
	/*
		includes(first,last,first2,last2)
		判断是否第二个容器是否被包含在第一个容器之中 
		被包含时返回值为1，否则返回值为0 
	*/ 
	cout << "After includes():" << endl;
	if(includes(ivc1.begin(),ivc1.end(),ivc2.begin(),ivc2.end()))
		cout << "Be include!" << endl;
	else
		cout << "Not be include!" << endl;
	cout << endl;
	
	/*
		lexicographical_compare(first,last,first2,last2)
		检查第一个范围 [first1, last1) 是否按字典序小于第二个范围 [first2, last2) 
			1.用 operator< 比较元素。
			2.用给定的二元比较函数 comp 比较函数。
		如果两个序列长度不同，并且
		短序列和长序列头部完全一样，
		例如example和examplee.
		那么，长度大的字典序比短序的大。
	*/
	cout << "After lexicographical_compare():" << endl;
	char name1[] = "limuge";
	char name2[] = "houyimei";	//按字典查找limuge比houyimei在后面 
	if(lexicographical_compare(name1,name1+6,name2,name2+8))
		cout << name1 <<" is less than " << name2 <<endl;
	else
		cout << name1 <<" is greater than " << name2 <<endl;	
	cout <<endl;
	if(lexicographical_compare(ivc1.begin(),ivc1.end(),ivc2.begin(),ivc2.end()))
		cout << "ivc1 is less than ivc2" <<endl;
	else
		cout << "ivc1 is greater than ivc2" <<endl;
	cout << endl;
	
	/*
		lower_bound(first,last,val)
		first和last分别指的是起始和终止的迭代器
		val指的是要查找的值,该函数的返回值是一个迭代器，返回大于等于val的第一个值的位置 
	*/
	cout << "After lower_bound(5):" << endl;
	int pos= lower_bound(ivc1.begin(), ivc1.end(), 5)-ivc1.begin();	//减去开始的位置迭代器，最终结果会是位置。 
	cout << pos << endl;
	cout << endl;
	
	/*
		upper_bound(first,last,val) 
		first和last分别指的是起始和终止的迭代器
		val指的是要查找的值,该函数的返回值是一个迭代器，返回大于等于val的最后的一个的位置 
		对应lower_bound()函数是upper_bound()函数，它返回大于等于key的最后一个元素
		也同样是要求容器，若数组中无重复元素，则两者返回值相同
	*/
	cout << "After upper_bound(5):" << endl;
	int ipos= upper_bound(ivc1.begin(), ivc1.end(), 5)-ivc1.begin();	//减去开始的位置迭代器，最终结果会是位置。 
	cout << ipos << endl;
	cout << endl;
	
	/*
		make_heap(first,last,参数)
		制造一个堆，可用伪函数less()，greater()来生成大顶堆和小顶堆 
		pop_heap(first,last)推出堆顶的元素,这里没有删除元素只是将堆顶元素和容器最后一个元素进行了替换 
		push_heap()将一个元素压进堆里,与make_heap用法差不多。 
 	*/
 	cout << "After make_heap(less()):" << endl;
 	make_heap(ivc2.begin(),ivc2.end(),less<int>());
 	for_each(ivc2.begin(),ivc2.end(),output);
 	cout << endl;
 	cout << "After make_heap(greater()):" << endl;
 	make_heap(ivc2.begin(),ivc2.end(),greater<int>());
 	for_each(ivc2.begin(),ivc2.end(),output);
 	cout << endl;
 	cout << "After push_heap(greater()):" << endl;
 	push_heap(ivc2.begin(),ivc2.end(),greater<int>());
 	for_each(ivc2.begin(),ivc2.end(),output);
 	cout << endl;
 	cout << "After pop_head():" << endl;
 	pop_heap(ivc2.begin(),ivc2.end());
 	for_each(ivc2.begin(),ivc2.end(),output);
 	cout << endl;
 	cout << "After sort_heap():" << endl;
 	sort_heap(ivc2.begin(),ivc2.end());
 	for_each(ivc2.begin(),ivc2.end(),output);
 	cout << endl;
 	cout << endl;
 	
 	/*
 		max_element(first,last)
		 返回first和last范围中最大值所在的位置 
		min_element(first,last)
		 返回first和last范围中最小值所在的位置  
	*/
	cout << "After max_element():" << endl;
	int max = max_element(ivc1.begin(),ivc1.end())-ivc1.begin();
	cout << max << endl;
	cout << "After min_element():" << endl;
	int min = min_element(ivc1.begin(),ivc1.end())-ivc1.begin();
	cout << min << endl;
	cout << endl;  	 
	
	/*
		merge(first,last,first2,last2,result)
		合并两个序列 ,result是存放合并后的序列容器开始的位置（即迭代器）
		注意要给存储数据的容器开辟空间，否则存不进去值 
	*/
	cout << "After merge():" << endl;
	vector<int> ivc3;
	ivc3.resize(ivc1.size()+ivc2.size()); 
	merge(ivc1.begin(),ivc1.end(),ivc2.begin(),ivc2.end(),ivc3.begin());
	for_each(ivc3.begin(),ivc3.end(),output);
	cout << endl; 
	cout << "内容就到这里结束了！，祝大家学业有成";
	return 0;
}

Hey, please read the content in the code segment carefully, all the dry goods are in the code segment.

The result after running is as follows:

 

 

Well, it's time for me to rush to the meditation class haha ​​I'm in a hurry, see you in the next blog.

 Everyone, work hard to overcome your own technical difficulties, come on, and shine in your respective fields! ! !