C++ vector清空元素的常用两种方法

C++ vector清空元素的常用两种方法

#include <iostream>
#include <vector>

using namespace std;


int main(int argc, char const *argv[])
{

	vector<int> vecnum;
    vecnum.push_back(1);
    vecnum.push_back(2);
    vecnum.push_back(3);
    vecnum.push_back(4);
    vecnum.push_back(5);
    vecnum.push_back(6);
    vecnum.push_back(7);

    //打印vector的大小和容量
    cout << "old: size = " << vecnum.size() << " ; capacity = " << vecnum.capacity() << endl;

    //1. clear()，清空元素，但不回收空间
    vecnum.clear();
    //打印vector的大小和容量
    cout << "clear():" << endl;
    cout << "last: size = " << vecnum.size() << " ; capacity = " << vecnum.capacity() << endl;

    vecnum.push_back(1);
    vecnum.push_back(2);
    vecnum.push_back(3);
    vecnum.push_back(4);
    vecnum.push_back(5);
    vecnum.push_back(6);
    vecnum.push_back(7);

    //2. 最简单的使用swap,清除元素并回收内存
    vector<int>().swap(vecnum);
    cout << "swap:" << endl;
    //打印vector的大小和容量
    cout << "last: size = " << vecnum.size() << " ; capacity = " << vecnum.capacity() << endl;



	return 0;
}