resize是设置向量的大小：即向量的大小与容量相同。而reserve是设置向量的容量，并不改变向量的大小。另外：向量的最大大小是固定住，不可改变。例子：

#include "stdafx.h"

#include <iostream>

#include <vector>

 

using namespace std;

 

typedefvector<int> VEC_INT;

int_tmain(int argc, _TCHAR* argv[])

{

    VEC_INTthevec;

    cout<<"before insert data:"<<endl;

    cout<<"the size of vector:"<<thevec.size()<<endl;

    cout<<"the capasity of vector:"<<thevec.capacity()<<endl;

    cout<<"the max size of vector:"<<thevec.max_size()<<endl;

    cout<<"after insert data:"<<endl;

    thevec.push_back(42);

    cout<<"the size of vector:"<<thevec.size()<<endl;

    cout<<"the capasity of vector:"<<thevec.capacity()<<endl;

    cout<<"the max size of vector:"<<thevec.max_size()<<endl;

 

    thevec.reserve(100);

    cout<<"After reserve (100):"<<endl;

    cout<<"the size of vector:"<<thevec.size()<<endl;

    cout<<"the capasity of vector:"<<thevec.capacity()<<endl;

    cout<<"the max size of vector:"<<thevec.max_size()<<endl;

 

    thevec.resize(1000);

    cout<<"After resize (1000):"<<endl;

    cout<<"the size of vector:"<<thevec.size()<<endl;

    cout<<"the capasity of vector:"<<thevec.capacity()<<endl;

    cout<<"the max size of vector:"<<thevec.max_size()<<endl;

    return 0;

}

运行结果：

可以看出：默认情况下，向量的大小和容量是相同的，如果用resize改变向量的大小，则同时改变了向量的容量。