関連ワード:  c++ unordered_map vector as key    c++ unordered_map vector    c++ unordered_map vector as value    c++ vector vs unordered_map    c++ unordered_map vs vector performance    c++ unordered_map vs vector of pairs    c++ unordered_map insert vector    c++ convert unordered_map to vector    c++ initialize unordered_map with vector    c++ insert vector into unordered_map