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Ternary Operator in C

The ternary operator (?:) in C is a type of conditional operator. The term "ternary" implies that the operator has three operands. The ternary operator is often used to put multiple conditional (if-else) statements in a more compact manner.

Syntax of Ternary Operator in C

The ternary operator is used with the following syntax −

exp1 ? exp2 : exp3

It uses three operands −

  • exp1 − A Boolean expression evaluating to true or false
  • exp2 − Returned by the ? operator when exp1 is true
  • exp3 − Returned by the ? operator when exp1 is false

Example 1: Ternary Operator in C

The following C program uses the ternary operator to check if the value of a variable is even or odd.

#include <stdio.h>

int main(){

   int a = 10;
   
   (a % 2 == 0) ? printf("%d is Even \n", a) : printf("%d is Odd \n", a);

   return 0;
}

Output

When you run this code, it will produce the following output −

10 is Even

Change the value of "a" to 15 and run the code again. Now you will get the following output −

15 is Odd

Example 2

The conditional operator is a compact representation of if–else construct. We can rewrite the logic of checking the odd/even number by the following code −

#include <stdio.h>

int main(){

   int a = 10;

   if (a % 2 == 0){
      printf("%d is Even\n", a);
   }
   else{
      printf("%d is Odd\n", a);
   }
   
   return 0;
}

Output

Run the code and check its output −

10 is Even

Example 3

The following program compares the two variables "a" and "b", and assigns the one with the greater value to the variable "c".

#include <stdio.h>

int main(){

   int a = 100, b = 20, c;

   c = (a >= b) ? a : b;

   printf ("a: %d b: %d c: %d\n", a, b, c);

   return 0;
}

Output

When you run this code, it will produce the following output −

a: 100 b: 20 c: 100

Example 4

The corresponding code with if–else construct is as follows −

#include <stdio.h>

int main(){

   int a = 100, b = 20, c;

   if (a >= b){
      c = a;
   }
   else {
      c = b;
   }
   printf ("a: %d b: %d c: %d\n", a, b, c);

   return 0;
}

Output

Run the code and check its output −

a: 100 b: 20 c: 100

Example 5

If you need to put multiple statements in the true and/or false operand of the ternary operator, you must separate them by commas, as shown below −

#include <stdio.h>

int main(){

   int a = 100, b = 20, c;

   c = (a >= b) ? printf ("a is larger "), c = a : printf("b is larger "), c = b;
   
   printf ("a: %d b: %d c: %d\n", a, b, c);

   return 0;
}

Output

In this code, the greater number is assigned to "c", along with printing the appropriate message.

a is larger a: 100 b: 20 c: 20

Example 6

The corresponding program with the use of if–else statements is as follows −

#include <stdio.h>

int main(){

   int a = 100, b = 20, c;

   if(a >= b){
      printf("a is larger \n");
      c = a;
   }
   else{
      printf("b is larger \n");
      c = b;
   }
   printf ("a: %d b: %d c: %d\n", a, b, c);

   return 0;
}

Output

Run the code and check its output −

a is larger
a: 100 b: 20 c: 100

Nested Ternary Operator

Just as we can use nested if-else statements, we can use the ternary operator inside the True operand as well as the False operand.

exp1 ? (exp2 ? expr3 : expr4) : (exp5 ? expr6: expr7)

First C checks if expr1 is true. If so, it checks expr2. If it is true, the result is expr3; if false, the result is expr4.

If expr1 turns false, it may check if expr5 is true and return expr6 or expr7.

Example 1

Let us develop a C program to determine whether a number is divisible by 2 and 3, or by 2 but not 3, or 3 but not 2, or neither by 2 and 3. We will use nested condition operators for this purpose, as shown in the following code −

#include <stdio.h>

int main(){

   int a = 15;
   printf("a: %d\n", a);

   (a % 2 == 0) ? ( 
      (a%3 == 0)? printf("divisible by 2 and 3") : printf("divisible by 2 but not 3"))
   : (
      (a%3 == 0)? printf("divisible by 3 but not 2") : printf("not divisible by 2, not divisible by 3")
   );
   
   return 0;
}

Output

Check for different values −

a: 15
divisible by 3 but not 2

a: 16
divisible by 2 but not 3

a: 17
not divisible by 2, not divisible by 3

a: 18
divisible by 2 and 3

Example 2

In this program, we have used nested if–else statements for the same purpose instead of conditional operators −

#include <stdio.h>

int main(){

   int a = 15;
   printf("a: %d\n", a);

   if(a % 2 == 0){
      if (a % 3 == 0){
         printf("divisible by 2 and 3");
      }
      else {
         printf("divisible by 2 but not 3");
      }
   }
   else{
      if(a % 3 == 0){
         printf("divisible by 3 but not 2");
      }
      else {
         printf("not divisible by 2, not divisible by 3");
      }
   }
   
   return 0;
}

Output

When you run this code, it will produce the following output −

a: 15
divisible by 3 but not 2
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