高效地使用std::map

#include <iostream>
#include <string>
#include <map>
using namespace std;typedef map<string, int>  M;
M m;
const char  K[] = "key";void fn1 () {auto p = m.insert({K, 0});  ++(p.first->second);
}void fn2 () {auto it = m.find(K);if (it != m.end()) ++(it->second);
}int main (int argc, char** argv) {if (argc == 1) fn1(); else fn2();cout << m[K] << '\n';
}

gcc version 12.2.0 (Debian 12.2.0-14+deb12u1) 不用加-std

加了-std=c++03可以编译通不过。:-)