qq_31805591的博客

记录个错误： vector<map<x, y>> _data; // wrong: auto lv = _data.size(); auto it0 = _data[lv - 1].begin(); auto it1 = _data[lv - 1].begin(); _data.push_back(map<x, y>()); // ok: auto lv = _data.size(); _data.push_back(map<x, y>()); auto