GATE CSE 2020 | Question: 46

Question

Consider the following C functions.

int fun1(int n) { static int i= 0;     if (n > 0) {        ++i;       fun1(n-1);    }   return (i); }

int fun2(int n) {    static int i= 0;    if (n>0) { i = i+ fun1 (n) ;       fun2(n-1) ;   } return (i); }

The return value of $\text{fun}2 (5)$ is _________

Comments

Note on Static Variables: https://gateoverflow.in/2176/gate-cse-2012-question-48?show=386635#c386635

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how much time should we give to such type of questions in exam ?

:(

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This ques is only based on observation. It will not take more than 3-4 min.
Recurse for n = 5, you will understand what this function is doing.

No need to recurse for other values. Simply apply mathematics.

Answer 1

This illustration of function calling and values may help😀

$$\mathbf{Fig: Tracing\; by\; tree\; method}$$ Now $f1(5),$ if we observe it increments $ ‘i\text{’}, n$ times so $f1(5)$ will return $5.$

Similarly, $f1(4)$ will increment $ ‘i\text{’}$ $4$ times but $ ‘i\text{’}$ being static (just one memory location for entire program run instead of different memory location across function calls), it′ll resume from its previous value of $5.$  So, $f1(4)$ returns $9\;[5+4]$

By the same logic $f1(3)$ will return $12\; [9+3],$

$f1(2)$ will return $14\; [12+2],$

$f1(1)$ will return $15\; [14+1].$

$\therefore$ Return value $i=55$ and hence $55$ is the output of $f2(5).$

Comments

Should we consider i as 2 variables

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yes

Answer 2

Answer is 55.it is calling static int , when calling fun1() next time, it will add with previous value.

 

Answer 3

Answer will be 55

As it is calling static int , when calling fun1() next time, it will add with previous value

Comments

add diagram of function calling it will be good.

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my only doubt is "every time we call fun1 , why does it not initialize i to zero in the first statement?and does it allocate space for a new variable " i " every time we call it, keeping the previous variables as it it or there is just one i...kindly explain how many variable i's will be allocated ?

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@RuhanMuzaffar

U mean this statement

static int i= 0;

why will it be initialized more than once? It is a static variable, which keep it's previous value for further calculation. right?

 

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yes , i ve got it, my bad, thanx anyway.......do i have to remove the coment or something?, i am new here