容器的分类与各种测试（三）——deque

deque是双端队列，其表象看起来是可以双端扩充，但实际上是通过内存映射管理来营造可以双端扩充的假象，如图所示

 

 比如，用户将最左端的buff用光时，map会自动向左扩充，继续申请并映射一个新的buff，右端同理。

例程

#include<stdexcept>
#include<string>
#include<cstdlib>
#include<stdio.h>
#include<algorithm>//sort,qsort
#include<iostream>
#include<ctime>
#include<deque>
using namespace std;

long get_a_target_long()
{
	long target = 0;
	cout<<"target(0~"<<RAND_MAX<<"):";
	cin>>target;
	return target;
}
string get_a_target_string()
{
	long target = 0;
	char buf[10];
	cout<<"target(0~"<<RAND_MAX<<"):";
	cin>>target;
	snprintf(buf, 10, "%ld", target);
	return string(buf);
}
int compareLongs(const void* a, const void* b)
{
	return (*(long*)a - *(long*)b);
}

int compareStrings(const void *a, const void *b)
{
	if(*(string*)a > *(string*)b)
		return 1;
	else if(*(string*)a < *(string*)b)
		return -1;
	else
		return 0;
}
void test_deque(long& value)
{
	cout << "\ntest_deque().......... \n";

	deque<string> c;  	
	char buf[10];

	clock_t timeStart = clock();								
	for(long i=0; i< value; ++i)
	{
		try 
		{
			snprintf(buf, 10, "%d", rand());
			c.push_front(string(buf));  	
		}
		catch(exception& p)
		{
			cout << "i=" << i << " " << p.what() << endl;	
			abort();
		}
	}
	cout << "milli-seconds : " << (clock()-timeStart) << endl;	
	cout << "deque.size()= " << c.size() << endl;  
	cout << "deque.front()= " << c.front() << endl;	
	cout << "deque.back()= " << c.back() << endl;	
	cout << "deque.max_size()= " << c.max_size() << endl;	


	string target = get_a_target_string();	
	timeStart = clock();			
	auto pItem = ::find(c.begin(), c.end(), target);//	显示指明使用#include<algorithm>中的find() or sort()
	cout << "std::find(), milli-seconds : " << (clock()-timeStart) << endl;		

	if (pItem != c.end())
		cout << "found, " << *pItem << endl;
	else
		cout << "not found! " << endl;	

	timeStart = clock();		
	::sort(c.begin(), c.end());		//	显示指明使用#include<algorithm>中的find() or sort()				
	cout << "c.sort(), milli-seconds : " << (clock()-timeStart) << endl;		
	c.clear();	 
}			
int main()
{
	long int value;
	cout<<"how many elements:";
	cin>>value;
	test_deque(value);
	return 0;
}

 运行结果

 

 

来源：https://www.cnblogs.com/area-h-p/p/12012617.html