C でネストされたマップを反復するにはどうすればよいですか?

std::map<std::string, std::map<std::string, std::string>> m;

// Example data
m["name1"]["value1"] = "data1";
m["name1"]["value2"] = "data2";
m["name2"]["value1"] = "data1";
m["name2"]["value2"] = "data2";
m["name3"]["value1"] = "data1";
m["name3"]["value2"] = "data2";

for (auto const &ent1 : m) {
  // ent1.first is the outer key
  for (auto const &ent2 : ent1.second) {
    // ent2.first is the inner key
    // ent2.second is the value
  }
}

for (auto const &[outer_key, inner_map] : m) {
  for (auto const &[inner_key, inner_value] : inner_map) {
    // Access outer_key, inner_key, and inner_value directly
  }
}

for (auto const &[outer_key, inner_map] : m) {
  for (auto const &[inner_key, inner_value] : inner_map) {
    // Access outer_key, inner_key, and inner_value without need for variables
  }
}