How can I pad a float with leading zeros when using cout << operator

问题

Putting together these questions:

How can I pad an int with leading zeros when using cout << operator?

Printing the correct number of decimal points with cout

How can I stream to std::cout, for example, this variable

double x = 7.1224

And make it look like this?

07.12

回答1:

Combine std::setw, std::setfill, std::fixed and std::setprecision:

std::cout << std::setfill('0') << std::setw(5) 
          << std::fixed << std::setprecision(2) << x;

So, the value for setw is: 2 for the precision desired + 2 for the integer desired + 1 for the floating point.

Note: x = 107.1224 will be outputted as 107.12.

来源：https://stackoverflow.com/questions/22509972/how-can-i-pad-a-float-with-leading-zeros-when-using-cout-operator