c++ - ordered_map() 中 ‘.’ 标记之前的预期主表达式

Question

我想插入段落或文章内容并处理每个单词。下面我试图获取每个字符串，然后获取它的出现。最后我想要出现次数最多的词。我是 C++ 的新手。现在我已经静态插入了两个字符串。这会给出错误 expected primary-expression before ‘.’ token。代码如下:`

#include <string>
#include <iostream>
#include <unordered_map>

int main()
{
    typedef std::unordered_map<std::string,int> occurrences;
    occurrences s1;
    s1.insert(std::pair<std::string,int>("Hello",1));
    s1.insert(std::pair<std::string,int>("Hellos",2));

    //for ( auto it = occurrences.begin(); it != occurrences.end(); ++it )  this also gives same + additional " error: unable to deduce ‘auto’ from ‘<expression error>’" error
    for (std::unordered_map<std::string, int>::iterator it = occurrences.begin();//Error is here
                                                    it != occurrences.end(); ////Error is here
                                                    ++it)
    {
        std::cout << "words :" << it->first << "occured" << it->second <<  "times";
    }

    return 0;
}

错在哪里？

Answer 1

occurrences 是一种类型，而不是对象。您想要使用对象 s1。

版本 1:

for (auto it = s1.begin(); it != s1.end(); ++it)

版本 2:

for (std::unordered_map<std::string, int>::iterator it = s1.begin(); it != s1.end(); ++it)

版本 3:

for (auto pair : s1)