hash_map的遍历
我这有段代码和注释了的代码
都是执行相同目的的操作：遍历删除自己。（我就是要遍历...不要说用clear)
你直觉认为谁更快吗？为什么呢?
#define _SECURE_SCL 0
#include <iostream>
#include <string>
#include <vector>
#include <list>
#include <sstream>
#include <iomanip>
#include <hash_map>
#include "windows.h"
using namespace std;
using stdext::hash_map;
void main()
{
hash_map<string,int> hm;
list<string> lst;
for (int i = 0; i < 30000; ++i)
{
stringstream ss;
ss<<setw(20)<<setfill('0')<<i;
lst.push_back(ss.str());
hm.insert(make_pair(ss.str(),i));
}
DWORD dwtickbeg = GetTickCount();
for (list<string>::iterator iter = lst.begin(); iter != lst.end(); ++iter)
{
hm.erase(*iter);
}
DWORD dwEnd = GetTickCount() - dwtickbeg;
//hash_map<string,int> hm;
//for (int i = 0; i < 30000; ++i)
//{
//stringstream ss;
//ss<<setw(20)<<setfill('0')<<i;
//hm.insert(make_pair(ss.str(),i));
//}
//DWORD dwtickbeg = GetTickCount();
//hash_map<string,int>::iterator iter = hm.begin();
//while (iter != hm.end())
//{
//iter= hm.erase(iter);
//}
//DWORD dwEnd = GetTickCount() - dwtickbeg;
cout<<dwEnd<<" "<<hm.size()<<endl;
system("pause");
return;
}
