# Practice 1

``````//要求用户以整数输入英寸为单位的身高，将其转换为英尺和英寸

#include <iostream>
using namespace std;

int main(){
const int foot = 12;
int inches = 0;
cin >> inches;
cout << "Your height is " << inches / foot <<  "feet and " << inches % foot << " inches!" << endl;
return 0;
}``````

# Practice 2

``````//以英尺英寸的形式输入身高，以磅为单位输入体重，计算BMI

#include <iostream>
using namespace std;

int main()
{
const int inches_per_foot = 12;
const double meters_per_inch = 0.0254;
const double kg_per_pound = 2.2;

//身高
int feet = 0;
int inches = 0;
cout << "Please enter your height: _ feet and _ inches:" << endl;
cin >> feet;
cin >> inches;
int height_by_inches = feet * inches_per_foot;
double height_by_meters = height_by_inches * meters_per_inch;
cout << "Your height is " << height_by_meters << " meters;" << endl;

//体重
double weight_by_pounds = 0.0;
cin >> weight_by_pounds;
double weight_by_kg = weight_by_pounds * kg_per_pound;
cout << "Your weight is " << weight_by_kg << " kg;" << endl;

//BMI
double bmi = weight_by_kg / (height_by_meters * height_by_meters);
cout << "Your BMI is " << bmi << endl;
return 0;

}``````

# Practice 3

``````//输入度分秒，以度数输出

#include <iostream>
using namespace std;

int main()
{
const int minutes_per_degree = 60;
const int seconds_per_minute = 60;

int degrees = 0;
double minutes = 0;
double seconds = 0;
cout << "Enter the degrees:" << endl;
cin >> degrees;
cout << "Enter the minutes:" << endl;
cin >> minutes;
cout << "Enter the seconds:" << endl;
cin >> seconds;

double seconds_to_minutes = seconds / seconds_per_minute;
//踩坑：int除以int一定得到整数(即使结果将会赋值给double)，因此上句参与运算的两个数必须要有一个是非int类型，否则上句结果为0
cout << "seconds_to_minutes: " << seconds_to_minutes << endl;
double minutes_to_degrees = (minutes + seconds_to_minutes) / minutes_per_degree;
cout << "minutes: " << minutes + seconds_to_minutes << endl;
double final_degrees = degrees + minutes_to_degrees;
cout << degrees << " degrees " << minutes << " minutes " << seconds << " seconds = "
<< final_degrees << " degrees" << endl;
return 0;
}``````

# Practice 4

``````//整数方式输入秒数，然后以天时分秒的方式输出

#include <iostream>
using namespace std;

int main()
{
const int hours_per_day = 24;
const int minutes_per_hour = 60;
const int seconds_per_minute = 60;

long long time_by_seconds = 0;
cout << "Please enter time by seconds:" << endl;
cin >> time_by_seconds;

long long time_by_minutes = time_by_seconds / seconds_per_minute;
int seconds = time_by_seconds % seconds_per_minute;

long long time_by_hours = time_by_minutes / minutes_per_hour;
int minutes = time_by_minutes % minutes_per_hour;

int time_by_days = time_by_hours / hours_per_day;
int hours = time_by_hours % hours_per_day;

cout << time_by_seconds << " seconds = " << time_by_days << " days "
<< hours << " hours " << minutes << " minutes " << seconds << " seconds;" << endl;

}``````

# Practice 5

``````//输入全球人口和国家人口，并计算百分比输出

#include <iostream>
using namespace std;

int main()
{
long long total = 0;
long long single = 0;
cout << "Please enter total population:" << endl;
cin >> total;
cin >> single;

long double double_single = (long double) (single);
//踩坑：强制类型转换不会修改变量自身，需要一个新变量来存储

double percent = (double_single / total) * 100;
//long long 为整型，所以必须将其中一个 long long 强制类型转换为 long double 后才能得到 double 类型结果

cout << "The percent is " << percent << endl;
return 0;
}``````

# Practice 6

``````//耗油量计算

#include <iostream>
using namespace std;

int main()
{
int calc_type = 0;
cout << "Enter 1 or 2 to choose type:" << endl;
cout << "1 - miles/gallon" << endl;
cout << "2 - liters/100km" << endl;
cin >> calc_type;

if (calc_type == 1) {
double miles = 0;
double gallons = 0;
cout << "Enter miles and gallons:" << endl;
cin >> miles;
cin >> gallons;
cout << "The fuel consumption is " << miles / gallons << " miles per gallon" << endl;
return 0;
} else if (calc_type == 2) {
double kms = 0;
double liters = 0;
cout << "Enter kms and liters:" << endl;
cin >> kms;
cin >> liters;
cout << "The fuel consumption is " << (liters * 100) / kms << " liters per 100km" << endl;
return 0;
} else {
cout << "Invalid input" << endl;
return 0;
}
}``````

# Practice 7

``````//耗油量转换

#include <iostream>
using namespace std;

int main()
{
const double miles_per_100km = 62.14;
const double liters_per_gallon = 3.875;
double eu_fuel_consumption = 0;
double us_fuel_consumption = 0;
cout << "Enter fuel consumption by eu: __ liters per 100km" << endl;
cin >> eu_fuel_consumption;
us_fuel_consumption = miles_per_100km / (eu_fuel_consumption / liters_per_gallon);
cout << "Fuel consumption by us is " << us_fuel_consumption << " miles per gallon" << endl;
return 0;
}``````

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