vector中resize和reserve的區別，代碼驗證

#include <vector>
using namespace std;


int main()
{
    vector<int>   resizeVect;
    vector<int>   reserveVect;

    resizeVect.resize(50, 2);         //立即分配50個int，每個值爲2，默認值爲0，如果是class默認構造函數
    vector<int>::iterator iter = resizeVect.begin();
    printf("out put resizeVect value start\n");
    for(; iter != resizeVect.end(); iter++)
    {
        printf("%d ", *iter);
    }
    printf("\nout put resizeVect value end\n");

    printf("resizeVect capacity %d \n", resizeVect.capacity());
    printf("resizeVect size %d \n", resizeVect.size());
    resizeVect.push_back(3);          //添加一個值後,超出了capacity，capacity增加一半
    printf("resizeVect capacity %d \n", resizeVect.capacity());
    printf("resizeVect size %d \n", resizeVect.size());


    printf("\r\n \r\n");


    reserveVect.reserve(50);          //預留capacity爲50，但是沒有內存，當然也不會有值
    iter = reserveVect.begin();
    printf("out put resizeVect value start\n");
    for(; iter != reserveVect.end(); iter++)
    {
        printf("%d ", *iter);
    }
    printf("\nout put resizeVect value end\n");

    printf("reserveVect capacity %d \n", reserveVect.capacity());
    printf("reserveVect size %d \n", reserveVect.size());
    reserveVect.push_back(3);         //添加一個值後，沒有超出capacity，capacity保持不變，size+1
    printf("reserveVect capacity %d \n", reserveVect.capacity());
    printf("reserveVect size %d \n", reserveVect.size());


    system("pause");
    return 1;

}