C++怎么统计map中key的数量

可以使用map的size()函数来统计map中key的数量。size()函数返回的是map中键值对的数量，即key的数量。以下是一个示例代码：

#include <iostream> #include <map>  int main() {     std::map<int, std::string> myMap;     myMap[1] = "Apple";     myMap[2] = "Banana";     myMap[3] = "Orange";      int keyCount = myMap.size();     std::cout << "The number of keys in the map is: " << keyCount << std::endl;      return 0; } 

输出结果为：

The number of keys in the map is: 3