c – 迭代器返回垃圾

参见英文答案 > Does resizing a vector invalidate iterators?????????????????????????????????????5个
无法弄清楚我哪里出错了.据我所知,这段代码应返回“1,2,3”,但我得到以下内容.我需要全局声明的向量及其迭代器,因为我将向量传递给实际代码中的函数,并且需要在某些函数中更新迭代器.任何帮助表示赞赏！

#include <iostream>
#include <vector>

using namespace std;

vector<float> grid;
vector<float>::iterator gridPtr;

int main()

{
  grid.push_back(1);
  grid.push_back(2);

  gridPtr = grid.begin();

  grid.push_back(3);

  cout << "gridPtr: " << *gridPtr << endl;

  gridPtr++;

  cout << "gridPtr: " << *gridPtr << endl;

  gridPtr++;

  cout << "gridPtr: " << *gridPtr << endl;
}

返回：

gridPtr: 2.62257e-33
gridPtr: 2
gridPtr: 0