c++ - 如何将 multimap 传递给函数

Question

我有一个非常简单的问题。我只是在学习 map 和多重 map ，想知道如何将它们传递给函数。我大部分时间都在思考多重映射，但想要一个简单的示例来说明如何将它们传递给 void 函数。

int main()
{
multimap<string,int> movies;


movies.insert(pair<string,int>("Happy Feet",6));
movies.insert(pair<string,int>("Happy Feet",4));
movies.insert(pair<string,int>("Pirates of the Caribbean",5));
movies.insert(pair<string,int>("Happy Feet",3));
movies.insert(pair<string,int>("Pirates of the Caribbean",4));
movies.insert(pair<string,int>("Happy Feet",4));
movies.insert(pair<string,int>("Flags of out Fathers",4));
movies.insert(pair<string,int>("Gigli",4));

cout<<"There are "<<movies.count("Happy Feet")<<" instances of "<<"Happy Feet"<<endl;
cout<<"There are "<<movies.count("Pirates of the Caribbean")<<" instances of "<<"Pirates of the Caribbean"<<endl;
cout<<"There are "<<movies.count("Flags of out Fathers")<<" instances of "<<"Flags of out Fathers"<<endl;
cout<<"There are "<<movies.count("Gigli")<<" instances of "<<"Gigli"<<endl;



system("PAUSE");
calculateAverage(movies);  // this is where im getting errors such as no conversions
return 1;
}
void calculateAverage(multimap<string,int> *q)
{
// this function wont calculate the average obviously. I just wanted to test it
int averageH;
int averageP;
int averageF;
int averageG;

averageH = (q->count("Happy Feet"));
averageP = (q->count("Happy Feet"));
averageF = (q->count("Happy Feet"));
averageG = (q->count("Happy Feet"));


};

Answer 1

为什么要通过指针传递？我认为最好传递一个引用(如果 map 应在函数内修改)或引用 const 否则

void calculateAverage(const multimap<string,int> & q)
{
// this function wont calculate the average obviously. I just wanted to test it
int averageH;
int averageP;
int averageF;
int averageG;

averageH = (q.count("Happy Feet"));
averageP = (q.count("Happy Feet"));
averageF = (q.count("Happy Feet"));
averageG = (q.count("Happy Feet"));
};