C++/Language/If
Содержание
Add an else part to the if statement
#include <iostream>
using namespace std;
int main(void)
{
int num;
cout << "Enter a whole number: ";
cin >> num;
if ( num % 2 == 0 )
cout << "The number is even" << endl;
else
cout << "The number is odd" << endl;
return 0;
}
Conditional Expressions
#include <iostream>
using namespace std;
int main()
{
float x, y;
cout << "Type two different numbers:";
if( !(cin >> x && cin >> y) ) {
cout << "\nInvalid input!" << endl;
}else {
cout << "\nThe greater value is: " << (x > y ? x : y) << endl;
}
return 0;
}
if /else if /else statement in action
#include <iostream>
using namespace std;
int main(void)
{
int testScore;
cout << "Enter your test score: ";
cin >> testScore;
if (testScore >= 90 )
cout << "Your grade is an A" << endl;
else if (testScore >= 80 )
cout << "Your grade is a B" << endl;
else if (testScore >= 70 )
cout << "Your grade is a C" << endl;
else if (testScore >= 60 )
cout << "Your grade is a D" << endl;
else
cout << "Your grade is an F" << endl;
return 0;
}
Nested if statement
#include <iostream>
#include <cstdlib>
using namespace std;
int main()
{
int magic;
int guess;
magic = rand(); // get a random number
cout << "Enter your guess: ";
cin >> guess;
if (guess == magic) {
cout << "** Right **\n";
cout << magic << " is the magic number.\n";
}
else {
cout << "...Sorry, you"re wrong.";
if(guess > magic)
cout <<" Your guess is too high.\n";
else
cout << " Your guess is too low.\n";
}
return 0;
}
Testing if Both Boolean Expressions Are True
#include <iostream>
using namespace std;
int main(void)
{
int age;
char choice;
bool citizen;
cout << "Enter your age: ";
cin >> age;
cout << "Are you a citizen (Y/N): ";
cin >> choice;
if (choice == "Y")
citizen = true;
else
citizen = false;
if (age >= 18)
if(citizen == true)
cout << "You are eligible to vote";
else
cout << "You are not eligible to vote";
else
cout << "You are not eligible to vote";
return 0;
}
Testing if Either Boolean Expression Is True
#include <iostream>
using namespace std;
int main(void)
{
int age;
cout << "Enter your age: ";
cin >> age;
if (age > 7)
if (age >= 70)
cout << "free";
else
cout << "You have to pay";
else
cout << "free";
return 0;
}
The use of if-else statements
#include <iostream>
using namespace std;
int main()
{
float x, y, min;
cout << "Enter two different numbers:\n";
if( cin >> x && cin >> y)
{
if( x < y )
min = x;
else
min = y;
cout << "\nThe smaller number is: " << min << endl;
}
else
cout << "\nInvalid Input!" << endl;
return 0;
}
Use an int value to control the if.
#include <iostream>
using namespace std;
int main()
{
int a, b;
cout << "Enter numerator: ";
cin >> a;
cout << "Enter denominator: ";
cin >> b;
if(b)
cout << "Result: " << a / b << "\n";
else
cout << "Cannot divide by zero.\n";
return 0;
}