C++容器——vector的reserve()和resize()踩坑记录

调bug搞了一晚上，发现坑在resize函数上。搜了一下相关的资料，做一下粗略的总结：

• reserve：预留容器capacity，但不改变size（不初始化）；
• resize：改变size（不改变容器原有元素，新增size部分初始化）；

#include <iostream>
#include <vector>
#include <string>
using namespace std;

int main() {
    vector<string> vecScore;
    vecScore.reserve(1);
    vecScore.push_back("test");
    vector<string>::iterator iter = vecScore.begin();
    while(iter != vecScore.end())
    {
        cout << *iter << endl;
        ++iter;
    }
    cout << "vector size after reserve: "<< vecScore.size() << endl;
    
    vecScore.resize(2);
    vector<string>::iterator iter1 = vecScore.begin();
    while(iter1 != vecScore.end())
    {
        cout << *iter1 << endl;
        ++iter1;
    }
    cout << "vector size after resize: "<< vecScore.size() << endl;
    
    vecScore.reserve(3);
    vector<string>::iterator iter2 = vecScore.begin();
    while(iter2 != vecScore.end())
    {
        cout << *iter2 << endl;
        ++iter2;
    }
    cout << "vector size after reserve again: "<< vecScore.size() << endl;

	return 0;
}

输出结果：

另外，vector初始化时：

vector<string> vecScore(1); 
//等效于
//vector<string> vecScore;
//vecScore.push_back("");

参考：
https://www.cnblogs.com/zhuruibi/p/8983192.html
https://blog.csdn.net/jinx_qixianzhi/article/details/83143748
http://www.cplusplus.com/reference/vector/vector/resize/