UGC NET CSE | December 2018 | Part 2 | Question: 51

Question

Consider the $C/C++$ function $f()$ given below:

void f(char w[])
{
    int x=strlen(w); //length of a string
    char c;
    for (int i=0; i<x; i++)
    {
        c=w[i];
        w[i]=w[x-i-1];
        w[x-i-1] =c;
    }
}

Which of the following is the purpose of $f()$ ?

• A. It outputs the contents of the array in reverse order
• B. It outputs the contents of the array in the original order
• C. It outputs the contents of the array with the characters shifted over by one position
• D. It outputs the contents of the array with the characters rearranged so they are no longer recognized as the words in the original phrase

Answer 1

let i be a position in array from left side, then (x-i-1) should be the i$^{th}$ position from the right.

When for loop starts, upto the mid point,

c = w[i]

w[i]=w[x-i-1]

w[x-i-1] = c

swaps the elements which are at i$^{th}$  and (x-i-1)$^{th}$ ===> reverse the input order.

 

From the mid point to end, again same code applied

reverse(revere of input order) = original order of input preserve at the end.

 

PS: let take input length(x)=7 ===> maximum index = 6 only due to strlen returns size of the string without null character.

when i=0, x-i-1=6 ==> a[0] swapped with a[6]

when i=6, x-i-1 =0 ==> a[6] swapped with a[0].

∴ original order preserved.