访问地图的值，它是一个向量对 C++

Question

I have a map declared by

map <string, vector<pair<int, string>>>;

As I iterate through the map I want to access the data in the vector to print out and do operations on, I've been trying to use myMap.at(string1).first to access the integer associated with the key string1 , but I keep getting type errors. Could someone explain the best way to access the data in this vector pair from its key?

Answer 1

Given:

map <string, vector<pair<int, string>>> myMap;

the:

myMap.at(string1).first

obviously should not compile. myMap.at() , if successfully matched with an associated value, will give you a vector . You are trying to use .first on that vector . vector s do not have .first and such members. Maybe you instead want:

map <string, pair<int, string>> myMap;

If you are sure that you want your original data type, accessing the first pair associated with string1 would be:

myMap.at(string1).at(0).first

This will fetch a vector<pair<int, string>> associated with string1 and give you the first element in the first pair of that vector.