C++ std :: vector :: data为什么返回的指针索引与矢量索引不匹配？

Question

我在http://www.cplusplus.com/reference/vector/vector/data/中找到了一个std :: vector的例子.

// vector::data
#include <iostream>
#include <vector>

int main ()
{
  std::vector<int> myvector (5);

  int* p = myvector.data();

  *p = 10;
  ++p;
  *p = 20;
  p[2] = 100;

  std::cout << "myvector contains:";
  for (unsigned i=0; i<myvector.size(); ++i)
    std::cout << ' ' << myvector[i];
  std::cout << '\n';

  return 0;
}

结果是

myvector contains: 10 20 0 100 0

我的问题可能很愚蠢,但我真的不明白这里发生了什么.我们直接指向了向量的内存.然后我们为第一个元素(索引0)赋值10,移动到第二个元素并为其赋值20(索引1).最后,我们为第三个元素(索引2)赋值100.答案应该如下吗？

10 20 100 0 0

Answer 1

这张照片可能有助于解释

int* p = myvector.data();
[   ] [   ] [   ] [   ] [   ]
  ^

*p = 10;
[10 ] [   ] [   ] [   ] [   ]
  ^

++p;
[10 ] [   ] [   ] [   ] [   ]
        ^

*p = 20;
[10 ] [20 ] [   ] [   ] [   ]
        ^

p[2] = 100; // [2] is relative to where p is
[10 ] [20 ] [   ] [100] [   ]
        ^