问题
I wrote a code like this:
int d{ 0 };
cin >> setw(2) >> d;
But it seems setw() has no effect on reading integers. If so, how we could implement behaviour of %2d of scanf() with istream?
回答1:
setw() is not designed to be used with integral types.
What would it do? Extract the last two decimal digits of the integer? What would happen if you had put std::hex into the stream?
The best approach is to read the number then deal with it yourself. For example, if you want to extract the least significant two digits, use d % 100 subsequently; making an extra correction for negative numbers.
来源：https://stackoverflow.com/questions/38920767/setw-does-not-affect-reading-integer-fields