为什么我无法使用索引访问字符串单个字符

Question

string strMap[8] = {"abc", "def", "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"};
//string digits received as parameter in function // digits = "234";

访问它如下：

int digitmapIndex = digits[index] - 46;   //index is some int 0,1 etc..
int mapstr_len = strMap[digitmapIndex];

或者

int mapstr_len = strMap[digits[index] - 46];

错误：

Line 25: Char 13: error: no viable conversion from 'std::string' (aka 'basic_string<char>') to 'int'
        int mapstr_len = strMap[digits[index] - 46];
            ^            ~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/bin/../lib/gcc/x86_64-linux-gnu/9/../../../../include/c++/9/bits/basic_string.h:816:7: note: candidate function
      operator __sv_type() const noexcept

Answer 1

这条线没有意义：

int mapstr_len = strMap[digitmapIndex];

strMap[digitmapIndex]是一个string对象，不能分配给int.

auto temp = strMap[digitmapIndex];

从temp，您可以通过索引访问其字符。