1 #pragma
 2 #include "pch.h"
 3 #include <iostream>
 4 #include<vector>
 5 #include<string>
 6 using namespace std;
 7 void fun1(int &a) {
 8     a = 10;
 9 }
10 int main(void)
11 {
12     vector<char> vec = {‘a‘,‘b‘,‘c‘,‘d‘,‘d‘, ‘d‘, ‘d‘, ‘d‘, ‘d‘, ‘d‘, ‘d‘, ‘d‘, ‘d‘, ‘d‘, ‘d‘, ‘d‘};
13     string str(vec.begin(), vec.begin()   1);
14     cout<<"1 element‘s capacity:"<<str.capacity();
15     cout << endl;
16     str.push_back(*(vec.begin()   1));
17     cout<<"two elements‘s capacity:"<<str.capacity();
18     for (int i = 0; i < 14; i  ) {
19         str.push_back(*(vec.begin()  2 i));
20     }
21     cout << endl;
22     cout << "15 elments‘s capacity:" << str.capacity();
23 }