矢量迭代器类型未知

我正在学习C++，这是我第一次使用迭代器

我已经写下了这段代码：

std::pair<max, max> ConvertToAStarMap::GetLimits(std::string map)
{
    // Init max and min variables.
    int max_x = std::numeric_limits<int>::min();
    int min_x = std::numeric_limits<int>::max();
    int max_y = max_x;
    int min_y = min_x;
    std::vector<std::string> map_cells = ConvertToAStarMap::split(map, ';');
    for (std::string::iterator it = map_cells.begin(); it != map_cells.end(); ++it)
}

我收到此错误：

ConvertToAStarMap.cpp: In member function ‘std::pair<max, max> ConvertToAStarMap::GetLimits(std::__cxx11::string)’:
ConvertToAStarMap.cpp:31:52: error: conversion from ‘std::vector<std::__cxx11::basic_string<char> >::iterator {aka __gnu_cxx::__normal_iterator<std::__cxx11::basic_string<char>*, std::vector<std::__cxx11::basic_string<char> > >}’ to non-scalar type ‘std::__cxx11::basic_string<char>::iterator {aka __gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char> >}’ requested
     for (std::string::iterator it = map_cells.begin(); it != map_cells.end(); ++it)
                                     ~~~~~~~~~~~~~~~^~
ConvertToAStarMap.cpp:31:59: error: no match for ‘operator!=’ (operand types are ‘std::__cxx11::basic_string<char>::iterator {aka __gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char> >}’ and ‘std::vector<std::__cxx11::basic_string<char> >::iterator {aka __gnu_cxx::__normal_iterator<std::__cxx11::basic_string<char>*, std::vector<std::__cxx11::basic_string<char> > >}’)
     for (std::string::iterator it = map_cells.begin(); it != map_cells.end(); ++it)
                                                        ~~~^~~~~~~~~~~~~~~~~~

怎么了？我不明白。