#include<iostream>#include<iomanip>using namespace std;int main(void){  double s;  cin>>s;    if(s*95>=300){    cout<<setiosflags(ios::fixed)<<setprecision(2)<<s*95*0.85<<endl;  }     else{    cout<<setiosflags(ios::fixed)<<setprecision(2)<<s*95<<endl;  }      return 0;}

Floating point output can be changed with<< setiosflags( ios::fixed ) : never use scientific notation //絕對不使用科學記數法。<< setiosflags( ios::scientific ) : always use scientific notation //使用科學記數法。<< resetiosflags( ios::floatfield ) : restores default (use fixed or scientific notation based on the precision)//重置為缺省。<< (re)setiosflags( ios::showpoint ) : controls if the trailing zeros and decimal point will be output (default is no) //控制小數點后面的零是否顯示。<< setprecision( digits ) : if fixed or scientific format is selected, controls the number of digits after the decimal place, otherwise controls the total number of significant digits// 如果fixed或者scientific已經確定了，則控制小數點后面的位數；否則，控制所有位數。

#include <iostream>#include <iomanip>using namespace std;int main(void){  double S = 0.000000123;  double A = 456.7;  double B = 8910000000000.0;  cout << "default precision is "     << cout.precision() << endl;  // 6  cout << "  S = " << S << endl;  // 1.23e-07  cout << "  A = " << A << endl;  // 456.7  cout << "  B = " << B << endl;  // 8.91e+12  cout << setiosflags(ios::showpoint)     << "ios::showpoint ON" << endl;  cout << "  S = " << S << endl;  // 1.23000e-07  cout << "  A = " << A << endl;  // 456.700  cout << "  B = " << B << endl;  // 8.91000e+12  cout << resetiosflags(ios::showpoint)     << "ios::showpoint OFF" << endl;  cout << setiosflags(ios::fixed)     << "ios::fixed ON" << endl;  cout << "  S = " << S << endl;  // 0.000000  cout << "  A = " << A << endl;  // 456.700000  cout << "  B = " << B << endl;  // 8910000000000.000000  cout << resetiosflags(ios::fixed)     << setiosflags(ios::scientific)     << "ios::scientific ON" << endl;  cout << "  S = " << S << endl;  // 1.230000e-07  cout << "  A = " << A << endl;  // 4.567000e+02  cout << "  B = " << B << endl;  // 8.910000e+12}