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STL/Vector Capacity And Reserve

STL/vector ˜ capacity ™€ reserve ํ•จˆ˜˜ ˜ˆ


ฒฐ

~cpp 
vector1— 100000 ฒˆ˜ ž… ฅ „ ํ•ฉ‹ˆ‹ค.
 €žฅ ณต„ ˜ˆ•ฝ€ ํ•˜€ •ŠŠต‹ˆ‹ค.
k: 0, new capacity: 1
k: 1, new capacity: 2
k: 2, new capacity: 4
k: 4, new capacity: 8
k: 8, new capacity: 16
k: 16, new capacity: 32
k: 32, new capacity: 64
k: 64, new capacity: 128
k: 128, new capacity: 256
k: 256, new capacity: 512
k: 512, new capacity: 1024
k: 1024, new capacity: 2048
k: 2048, new capacity: 4096
k: 4096, new capacity: 8192
k: 8192, new capacity: 16384
k: 16384, new capacity: 32768
k: 32768, new capacity: 65536
k: 65536, new capacity: 131072

ด œ vector2— ฐ™€ ž… ฅ„ ํ•ฉ‹ˆ‹ค.
‹จ,  €žฅ ณต„˜ ˜ˆ•ฝ„ ˆ˜ํ–‰ํ•ฉ‹ˆ‹ค.(100000).

†ŒŠค

~cpp 
#include <iostream>
#include <vector>
using namespace std;

/********************************************************/
/* ด ํ”„กœทธžจ€ STL Tutorial and Reference Guid 2nd ˜ */
/* 6.6 ˜ˆ œ ž…‹ˆ‹ค.									    */
/* ํ•œ€ํ™”™€ „„ ฒจ€ํ–ˆŠต‹ˆ‹ค.                        */
/*  €ž‘ถŒ€ ํ•ด‹ …— ”ฐฆ…‹ˆ‹ค.                         */
/********************************************************/

//  €žฅํ•  žฃŒํ˜•
class U{
public:
	unsigned long id;
	U():id(0){}
	U(unsigned long x):id(x){}
};

int main()
{
	cout << "STL Vecotr˜ capacity™€ reserve— Œ€ํ•œ ํ•จˆ˜ ˆ˜ํ–‰„ ณดž…‹ˆ‹ค." 
		<< endl;

	int N = 100000; // vector— ž… ฅ  žฃŒ˜ size
	vector<U> vector1, vector2;

	cout << "vector1— " << N << " ฒˆ˜ ž… ฅ „ ํ•ฉ‹ˆ‹ค. \n"
		<< " €žฅ ณต„ ˜ˆ•ฝ€ ํ•˜€ •ŠŠต‹ˆ‹ค.\n";

	int k;
	for ( k = 0; k!= N; ++k){
		vector<U>::size_type cap = vector1.capacity();
		vector1.push_back(U(k));
		if( vector1.capacity() != cap )
			cout << "k: " << k << ", new capacity: " 
				<< vector1.capacity() << "\n";
	}

	vector2.reserve(N);
	cout << "\nด œ vector2— ฐ™€ ž… ฅ„ ํ•ฉ‹ˆ‹ค.\n"
		<< "‹จ,  €žฅ ณต„˜ ˜ˆ•ฝ„ ˆ˜ํ–‰ํ•ฉ‹ˆ‹ค.(" << N << ").\n";
	
	
	for ( k = 0; k!= N; ++k){
		vector<U>::size_type cap = vector2.capacity();
		vector2.push_back(U(k));

		// ˜ˆ•ฝ ˜–ด žˆœ€กœ, —ฌธฐ— „ž…ํ•˜€ •ŠŠต‹ˆ‹ค.
		if ( vector2.capacity() != cap )
			cout << "k: " << k << ", new capacity: " 
				<< vector2.capacity() << "\n";
	}
	
	return 0;
}
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