Câu lệnh If else trong C++ | Học C++ cơ bản

if(Điều kiện){
  Statement(s);
}

<iostream>
using namespace std;
int main(){
  int num=70;
  if( num < 100 ){
     /* This cout statement will only execute,
      * if the above condition is true
      */ 
     cout<<"number is less than 100";
  }

  if(num > 100){
     /* This cout statement will only execute,
      * if the above condition is true
      */ 
     cout<<"number is greater than 100";
  }
  return 0;
}

number is less than 100

if(Điều Kiện 1) {
   Statement1(s);

   if(Điều kiện 2) {
      Statement2(s);
   }
}

<iostream>
using namespace std;
int main(){
   int num=90;
   /* Nested if statement. An if statement
    * inside another if body
    */
   if( num < 100 ){
      cout<<"number is less than 100"<<endl;
      if(num > 50){
         cout<<"number is greater than 50";
      } 
   }
   return 0;
}

number is less than 100
number is greater than 50

if(Điều kiện) {
   Statement(s);
}
else {
   Statement(s);
}

<iostream>
using namespace std;
int main(){
   int num=66;
   if( num < 50 ){
      //This would run if above condition is true
      cout<<"num is less than 50";
   }
   else {
      //This would run if above condition is false
      cout<<"num is greater than or equal 50";
   }
   return 0;
}

num is greater than or equal 50

if(Điều kiện 1) {
   /*if condition_1 is true execute this*/
   statement(s);
}
else if(Điều kiện 2) {
   /* execute this if condition_1 is not met and
    * condition_2 is met
    */
   statement(s);
}
else if(Điều kiện 3) {
   /* execute this if condition_1 & condition_2 are
    * not met and condition_3 is met
    */
   statement(s);
}
.
.
.
else {
   /* if none of the condition is true
    * then these statements gets executed
    */
   statement(s);
}

<iostream>
using namespace std;
int main(){
   int num;
   cout<<"Enter an integer number between 1 & 99999: ";
   cin>>num;
   if(num <100 && num>=1) {
      cout<<"Its a two digit number";
   }
   else if(num <1000 && num>=100) {
      cout<<"Its a three digit number";
   }
   else if(num <10000 && num>=1000) {
      cout<<"Its a four digit number";
   }
   else if(num <100000 && num>=10000) {
      cout<<"Its a five digit number";
   }
   else {
      cout<<"number is not between 1 & 99999";
   }
   return 0;
}

Enter an integer number between 1 & 99999: 8976
Its a four digit number