Thanks for the good response to my post Tricky questions or Puzzles in C. In this post, I will add some more Tricky questions or puzzles that are frequently asked in interviews by many good companies.
1) Function pointers : Function pointers are the topic that looks easy to understand but it's not, that's why it is a common topic to be asked in interviews by companies. So what is the tricky part here? Well, we will see with examples Let's look at some different types of function pointers examples :
a) int (*func)( ): This is the normal function pointer example in which func is a pointer to a function that returns int
b) int **func( ) : This is a normal function whose return type is pointer to pointer to int (Please keep in mind this is not a function pointer but it is just a normal function)
c) int *(*func)( ): Now this is different from b as there are parentheses now and it makes a difference. So Please don't be confused. Here func is a pointer to a function whose return type is a pointer to int
d) int (*func[])( ) : Here func is array of pointers to function which returns int
e) int *(*func())[] : People often get confused here in interviews. Here func is a pointer to a function whose return type is a pointer to an int array.
Also, check my blog post on Tricky Puzzles in JAVA below for Interviews.
Tricky Questions or puzzles in JAVA
2) Macros: Macros are simple yet tricky units of programming. Although it is not advisable to use a macro in programming it is one of the favorite topics in interviews to confuse people. So better be clear in it before going to interview. Now how is it tricky? Let's see some of the examples of Macros
a) #define Mul (X,Y) X*Y
z= Mul (3+5,8+2);
printf("%d",z);
Now, what will be the answer?. I assume most of you must be knowing the trick here but for those who don't let me tell you that answer will not be 80 as most of you might be thinking. The answer is 45. How?
when you call Mul (3+5,8+2) it substituted the value as it is in X*Y that is 3+5*8+2. So now 5*8 will be evaluated first followed by adding 3 and 2.
b) #define Mul (X,Y) X*Y
z= Mul (3+5,8+2)%2;
printf("%d",z);
What will be the answer now? will it be like z=45%2? Actually No. I myself made mistake in one of the interviews in this question. Again macros will substitute first and then evaluate. So z=3+5*8+2%2. Here % will evaluate first due to associativity and the answer will be 43.
Similarly, interviewers can change small things in this type of problem and can play with you in an interview. So try to modify the above problems in your compiler and check the output. The only thing you have to remember in macro is a substitute and then evaluate.
Also, see :
Tricky questions or puzzles in C part 3
Tricky examples on calculating the size of class
Best of Luck with the Interviews :-)
1) Function pointers : Function pointers are the topic that looks easy to understand but it's not, that's why it is a common topic to be asked in interviews by companies. So what is the tricky part here? Well, we will see with examples Let's look at some different types of function pointers examples :
a) int (*func)( ): This is the normal function pointer example in which func is a pointer to a function that returns int
b) int **func( ) : This is a normal function whose return type is pointer to pointer to int (Please keep in mind this is not a function pointer but it is just a normal function)
c) int *(*func)( ): Now this is different from b as there are parentheses now and it makes a difference. So Please don't be confused. Here func is a pointer to a function whose return type is a pointer to int
d) int (*func[])( ) : Here func is array of pointers to function which returns int
e) int *(*func())[] : People often get confused here in interviews. Here func is a pointer to a function whose return type is a pointer to an int array.
Also, check my blog post on Tricky Puzzles in JAVA below for Interviews.
Tricky Questions or puzzles in JAVA
2) Macros: Macros are simple yet tricky units of programming. Although it is not advisable to use a macro in programming it is one of the favorite topics in interviews to confuse people. So better be clear in it before going to interview. Now how is it tricky? Let's see some of the examples of Macros
a) #define Mul (X,Y) X*Y
z= Mul (3+5,8+2);
printf("%d",z);
Now, what will be the answer?. I assume most of you must be knowing the trick here but for those who don't let me tell you that answer will not be 80 as most of you might be thinking. The answer is 45. How?
when you call Mul (3+5,8+2) it substituted the value as it is in X*Y that is 3+5*8+2. So now 5*8 will be evaluated first followed by adding 3 and 2.
b) #define Mul (X,Y) X*Y
z= Mul (3+5,8+2)%2;
printf("%d",z);
What will be the answer now? will it be like z=45%2? Actually No. I myself made mistake in one of the interviews in this question. Again macros will substitute first and then evaluate. So z=3+5*8+2%2. Here % will evaluate first due to associativity and the answer will be 43.
Similarly, interviewers can change small things in this type of problem and can play with you in an interview. So try to modify the above problems in your compiler and check the output. The only thing you have to remember in macro is a substitute and then evaluate.
Also, see :
Tricky questions or puzzles in C part 3
Tricky examples on calculating the size of class
Best of Luck with the Interviews :-)
thank you so much sir. Expecting more MCQs on pointers and arrays.
ReplyDeleteSure will post it soon :)
ReplyDeleteSure will post it soon :)
ReplyDelete