C++ if else 条件语句的使用方法

C++ if else 条件语句的使用方法

if()
{ 
}
else if ()
{
}

普通的if(条件1 ||　条件二)中如果条件１满足的话就不会再判断条件二是否满足了，而是直接执行if后面的语句了

实例if

#include <iostream>
using namespace std;
 
int main() { 
  int a, b, c; 
 
  a = 2; 
  b = 3; 
 
  if(a < b)
     cout << "a is less than bn";
 
  if(a == b)
     cout << "you won't see thisn"; 
 
  cout << "n";
 
  c = a - b;
 
  cout << "c contains -1n";
  if(c >= 0)
     cout << "c is non-negativen";
  if(c < 0)
     cout << "c is negativen";
 
  cout << "n";
 
  c = b - a; // c now contains 1
  cout << "c contains 1n";
  if(c >= 0)
     cout << "c is non-negativen";
  if(c < 0)
     cout << "c is negativen";
 
  return 0;
}

当然我们还有if else

实例

#include <iostream>
 
 int main()
 {
     int firstNumber, secondNumber;
     std::cout << "Please enter a big number: ";
     std::cin >> firstNumber;
     std::cout << "nPlease enter a smaller number: ";
     std::cin >> secondNumber;
     if (firstNumber > secondNumber)
         std::cout << "nThanks!n";
     else
         std::cout << "nOops教程. The second is bigger!";
     return 0;
 }

多重

#include <iostream>
 
 int main()
 {
     int firstNumber =2;
     int secondNumber = 3;
 
     if (firstNumber >= secondNumber)
     {
         if ( (firstNumber  secondNumber) == 0) // evenly divisible?
         {
             if (firstNumber == secondNumber)
                 std::cout << "They are the same!n";
             else
                 std::cout << "They are evenly divisible!n";
         }
         else
             std::cout << "They are not evenly divisible!n";
     }
     else
         std::cout << "Hey! The second one is larger!n";
     return 0;
 }
 
Hey! The second one is larger!
 
if else if实例

#include <iostream>
using namespace std;
 
int main()
{
  int x;
 
  for(x=0; x<6; x++) {
    if(x==1) cout << "x is onen";
    else if(x==2) cout << "x is twon";
    else if(x==3) cout << "x is threen";
    else if(x==4) cout << "x is fourn";
    else cout << "x is not between 1 and 4n";
  }
 
  return 0;
}