std::to

c语言一般格式化用sprintf，c++却没有合适的函数，今天想到一种转日期的方式如下

int year = 2022;
int mon = 7;
int day = 12;
std::string str;
str += std::to_string(year/1000);
str += std::to_string(year/100%10);
str += std::to_string(year/10%10);
str += std::to_string(year%10);
str += "-";
str += std::to_string(mon/10);
str += std::to_string(mon%10);
str += "-";
str += std::to_string(day/10);
str += std::to_string(day%10);
std::cout< 
虽然麻烦一点但是在某些环境下可能能用到