ISRO CSE 2014 | Question: 47

Question

The following three 'C' language statements is equivalent to which single statement?

y=y+1;
z=x+y;
x=x+1

• A. z = x + y + 2;
• B. z = (x++) + (++y);
• C. z = (x++) + (y++);
• D. z = (x++) + (++y) + 1;

Answer 1

Here y is incrementing before calculation of z and x incrementing after calculation of z

So y will be preincrement and x is postincrement

So Ans B)

Answer 2

Just take x,y,z =1 and apply to all the options .

B and C will give correct answer

But as Y is incremented before X, and we are only using updated value of Y to find value of Z, so we will only choose B)

Answer is B).

Comments

why not option a ??

Answer 3

as u can see here the increment of y is written before z expression so preincrement ,

and then x is incremented after z expression so post increment

thats why ans will be x= ++y + x++

Answer 4

option B is right answer  (Upvote it if it is helpfull) 

B. z = (x++) + (++y);

here we need to perform stack evaluation 

so for the stack evalution the steps are

1. pre increment/ decrement
2. substitute the value 
3. Assign the values
4. post increment/ decrement

let x=1 y=2 

then by,

y=y+1; → y = 2 + 1 = 3 ;

z=x+y; → z = 1 + 3 = 4 ;

x=x+1; → x = 1 + 1 = 2 ;

after operations x=2,y=3,z=4………………….….,,,,….(1)

option B : x=1,y=2,z=3;

z = (x++) + (++y);

z = 1 + 3

z = 4

after assignment of value in z 

the value of y = 3 , x= 2  ,z=4  ………………………………...(2)

from eqn (1) & (2),

x,y,z values  are same