Microsoft Coding Interview Question! | Excel Sheet Column Number - Leetcode 171

FAANG Coding Interviews / Data Structures and Algorithms / Leetcode

[GregHogg]

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[georgetolis]

A different approach to this is starting from the start of the string and using the ascii conversion, char - 64, that A would be equal to 1, B to 2 and so on. We would enter with a sum = 0 and every loop we multiply sum by 26 and add the new letters value, similar to a conversion from a base 26 number system to decimal.

[raghavwastaken]

If we assume it is a 26 base number and instead of using a hash map, we can just use the (ASCII - 65) to get the value of that position, it's just the same as binary to decimal conversion and add 1 at end

[davidespinosa]

res = 0
for d in columnTitle:
res = 26 * res + ord(d) - ord('A') + 1
return res

[Spartan-gow]

For x in range(1, 1001):
Print (' thank you for the content ')

[mrt_]

why a hashmap? you can literally use the ascii value to calculate it. Example in python:
def to_number(code: str) -> int:
total = 0
length = len(code)
A = ord('A')
Z = ord('Z')
for idx, chr in enumerate(code):
c = ord(chr.upper())
if c < A or c > Z: return -1 # Invalid input
num = c - A + 1
total += 26 ** (length - (idx + 1)) * num
return total

you can also iterate through it backwards if you don't want to do (length - (idx + 1)) and instead want to do (idx)

[beetaylor]

I would use a spightly different approach, skipping the hashmap step

If you convert each character to their ascii representative, subtract 65 (ascii for capital A), then handle it as a number in base 26 you need to convert to base 10

[Arrow]

On a side note: If it is really referring to Excel columnames, then there is a maxvalue of "XFD" (= 2 ^ 14). But the basic principle could be extended.

[niklashaas]

Instead of going backwards you could also apply horners method

[senior]

This is the same logic when encoding a shuffle of deck of cards into a number. So you can have shuffle 1, 2, 3, ... 52! and each number corresponds to a specific configuration of a deck.

[dial-upking]

A lot of people have already pointed out the ASCII conversion, but here's the code if anyone was wondering. Sorry it's in Java. I'm more accustomed to it. :P
I'm also aware of the limitations due to short, but if you have more than 32, 767 columns, what are you doing?

String columnTitle = "ZY";
short num = 0, m = 1;
int i = columnTitle.length();
while (i > 0) {
num += (columnTitle.charAt(--i) - 64) * m;
m *= 26;
}
System.out.println(num); //Outputs 701

[robertsandiford]

Instead of going backwards you can multiply m by (length - pos)

[GM-reaper]

Wouldnt using a simple 29 element array would be better, or just using ascii convertions?

[pierceclemmons]

Wouldn't it be easier to treat the string as a base 26 number system? I mean I get that's what the answer is gonna get ya no matter what but I always do my different base number systems from the highest place value

[Sprezzatura]

For mentioning hash map you will get huge minus on coding interview. Iterating backwards is also will likely give you a minus

[Darkpill-]

Not surprised to hear it’s easy to get into Microsoft. 😂😂😂😂

[IsaacAlcocer]

Why are you starting from the back, is this a question with: * use a hashmap? or similar... maybe is just me but i cannot see why would you start from the back.

[amirdashti]

You forgot to mention it's just 26 conversation

[ichiroutakashima]

Interviewer: Let's say you have a problem with your manager. How are you...
Me: I'll use a hash map!

[phill]

Unintutive trick? Maybe if you never went to a maths class