Interview With Google.

Recently I have attended telephonic Interview with Google for the post of Sr. S/W Engineer in their internal application team. Someone named XYZ called me from their Mountainview office. It was around 10:30 PM (was already feeling sleepy). He started with asking me something about my previous projects and asked most challenging work i have done so far. Then he asked me about the languages i am comfortable with.
Then he asked whether i have used Microsoft Excel. Then he asked me the logic to convert column headers in excel sheet to numbers. Something like (A->1, B->2.......Z->26, AA->27 ....). Given the column header it should return the number mapping to it.
My answer was to use the number system with base 26. Store the column header in a string and extract each character and do ch-'A'+1(ascii diff) to get the index value corresponding to the number and multiply it with 26 ^(character positon -1) and add it to the result.

He accepted the answer and asked me to write the code for the same. I have written it in C and dictated it to him on phone. He then asked me to calculate the complexity of the same. I gave both the space and time complexity of my algorithm.

Next he asked me the logic to find the Square root of the number without using Square root function.

I gave him the numerical method answer... (Thank god i still remember some of my numerical method classes which i attended 8 years back). My answer was something like below.

double guess = num/2, oldguess = 0;
while(guess != oldguess) {
oldguess = guess;
guess = (num/guess + guess)/2;
}
return guess;

He was happy with my answer and asked me about the possible test cases i will have for it.
I gave him 0,1, negative numbers and numbers out of double range.. etc..............
He said excellent.
During the course of interview he was saying only few words like sounds good, make sense, excellent etc..

He then said he is done from his side and enquired whether i have any questions for him.
After one hour i got a chance to make him talk.... so i don't want to miss this opportunity and asked him about the kind of work they do ? Their work culture? etc... (even though i know answers from them.. :-))

He replied back saying G is a great company and talked about 20% time which we can use for personal projects... blah..blah .. blah...

Next day i got a call from their HR asking for my time for the onsite inerviews.....

Will keep posting my further rounds here.. .. do let me know the feedback..