vectorに要素を追加するコードと実行結果

#include <stdio.h>
#include <vector>

using namespace std;

int main()
{
	vector<int> vec;
	printf("size = %d, capacity = %d\n",
		 vec.size(), vec.capacity());
	
	for(int i = 0; i < 10; i++){
		vec.push_back(i);
	}
	printf("size = %d, capacity = %d\n",
		 vec.size(), vec.capacity());
	
	vec.reserve(300);
	printf("size = %d, capacity = %d\n",
		 vec.size(), vec.capacity());
	
	return 0;
}

実行結果
size = 0, capacity = 0
size = 10, capacity = 256
size = 10, capacity = 300