Gate CS

Question

#include<stdio.h>

int main()
{
    int x, y = 7;
    x = ++y + ++y + y--;
    printf("%d\n", x);
    return 0;
}

What is the output of this code snippet ?

A. 27

B. 26

C. 25

D. Compilation error

 

Comments

https://www.geeksforgeeks.org/sequence-points-in-c-set-1/

See here might it will help you to understand. It is a sequence point problem

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A). 27

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https://gateoverflow.in/62411/undefined-behaviour-in-c

Answer 1

Answer is A. 27

Comments

Can you please explain?

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Pre increamen have higher priority than all other operators so first they will increment after that binary operators will operate then after completion of that instruction i.e when control will transfer to next line ...post decrement operator will decrease y value ...

Y=>8 ==>9==>8...

9+9+9=27

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@talha hashim

Then according to you,

if x = ++y + y-- ;

then it should be y => 8 ==> 7

and x = 8 + 8 = 16...right?

But it gives 15. Why?

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please avoid discussion on Undefined Behavior in C

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There are 10 kinds of people in world - one who understand undefined behaviour and one who doesn't :)

Answer 2

(y=7)

y--  -->y=7( y=y-1 will be perform at last)

++y -->y=y+1=7+1=8

(y=8, updated)

++y  -->y=8+1=9

(y=9, updated)

now x=y+y+y ----->(++y + ++y +y--)

x=9+9+9=27

now y=y-1 will be implemented

y=9-1=8

 

x=27,y=8

Comments

@balaganesh

Then according to you,

if x = ++y + y-- ;

then it should be y => 8 ==> 7

and x = 8 + 8 = 16...right?

But it gives 15. Why?

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After your question i have checked with various examples, I came to know that its depends upon the compiler.