Classification containers with a variety of tests (four) - map

set the difference between the map and that the former key and value are separated, the former does not repeat key, value can repeat; the latter is the key value, the latter value must be unique . There, map may be used when inserted into [] of (insert when viewed code), which uses a look for insertion elements such as array interpolation method.

 

 Routine

#include<stdexcept>
#include<string>
#include<cstdlib>
#include<cstdio>
#include<algorithm>
#include<iostream>
#include<ctime>
#include<map>
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_map(long& value)
{
	cout << "\ntest_map().......... \n";

	map<long, string> c;  	
	char buf[10];

	clock_t timeStart = clock();								
	for(long i=0; i< value; ++i)
	{
		try
		{
			snprintf(buf, 10, "%d", rand());
			c [i] = string (buf); // insert on the performance of such an array of values, and actually i buf automatically synthesized in the inside thereof a pair of insert					
		}
		catch(exception& p) 
		{
			cout << "i=" << i << " " << p.what() << endl;	
			abort();
		}
	}
	cout << "milli-seconds : " << (clock()-timeStart) << endl;	
	cout << "map.size()= " << c.size() << endl;	//元素个数
	cout << "map.max_size()= " << c.max_size() << endl;		

	long target = get_a_target_long();		
	timeStart = clock();		
	auto pItem = c.find(target);								
	cout << "c.find(), milli-seconds : " << (clock()-timeStart) << endl;		 
	if (pItem != c.end())
		cout << "found, value=" << (*pItem).second << endl;
	else
		cout << "not found! " << endl;			
}
int main ()
{
	long int value;
	cout<<"how many elements: ";
	cin>>value;
	test_map(value);
	return 0;
}

 operation result