在《演算法競賽入門經典》一書中 習題1-5 打折 （discount）一件衣服95元，若消費滿300元，可打八五折。輸入購買衣服件數，輸出需要支付的金額（單位：元），保留兩位小數。 我編寫的代碼為 #include<iostream> #include<iomanip> using namespace ...
在《演算法競賽入門經典》一書中 習題1-5 打折 （discount）
一件衣服95元，若消費滿300元，可打八五折。輸入購買衣服件數，輸出需要支付的金額（單位：元），保留兩位小數。
我編寫的代碼為
#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; }
於是將C++中如何顯示不同格式的小數查了一下：
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)//重置為預設。 << (re)setiosflags( ios::showpoint ) : controls if the trailing zeros and decimal point will be output (default is no) //控制小數點後面的零是否顯示。 << 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，則控制小數點後面的位數；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 }
輸出為：
default precision is 6
S = 1.23e-007
A = 456.7
B = 8.91e+012
ios::showpoint ON
S = 1.23000e-007
A = 456.700
B = 8.91000e+012
ios::showpoint OFF
ios::fixed ON
S = 0.000000
A = 456.700000
B = 8910000000000.000000
ios::scientific ON
S = 1.230000e-007
A = 4.567000e+002
B = 8.910000e+012
--------------------------------
Process exited after 0.02482 seconds with return value 0
請按任意鍵繼續. . .
參考
https://www.cs.duke.edu/courses/cps149s/fall99/resources/n2.html
