Today I came across a question that is simple enough for most developers to solve fast, but just slightly complex enough to worth a little bit of discussion. I believe this questions, and my answer to it, is a pretty good demonstration why leetcode style interview exists. Let's look at the problem first:
https://leetcode.com/problems/isomorphic-strings/
The real problem at hand is how do you confirm whether two strings are representationally the same. Representationally, sorry for the unclear diction, because you can transform the strings into a representations of the order of appearance and how many of different kinds in each word.
so essentially, a good way to show an isomorphic representation of a string would be like:
egg = 122
add = 122
therefore egg and add are isomorphic
isomorphic = 1234356718;
Please see code below:
var isIsomorphic = function(s, t) {
if (!s || !t) return false;
if(s.length !== t.length) return false;
let sMap = {};
let tMap = {};
let sNumString = '';
let tNumString = '';
let currentS = '';
let currentT = ''
for (let i=0; i<s.length; i++) {
currentS = s[i];
currentT = t[i];
if(!sMap[currentS]) {
sMap[currentS] = Object.keys(sMap).length + 1
}
else {
sNumString += sMap[currentS]
}
if(!tMap[currentT]) {
tMap[currentT] = Object.keys(tMap).length + 1
}
else {
tNumString += tMap[currentT]
}
}
return sNumString === tNumString
};
I think questions like one this really digs deep into whether a developer really knows and is skillful at general problem solving and would be an indicator whether the employee will be good for the company.
(Although I don't know if my solution to this would be well-received at interviews when it is usually not possible to test the validity of code.)
I really dislike problems that are very esoteric and dependent on contextual knowledge. For example, you'd need to know a specific formula for solving how many prime numbers are in [0 ... n]. This type of problem is just terrible and not worthwhile to learn.
Another reason why I like the isomorphic string problem so much, because not only it is knowledge independent, but also does not require a huge mental aerobatic like https://leetcode.com/problems/maximum-subarray/
I would say, however, questions like maximum-subarray do show whether a candidate has reach a higher level of computational, emphasis here, solving skill. Except that in interviews, it's hugely frustrating if you haven't seen a problem remotely similar beforehand.
Do you have a similar question in mind that is like this one ? Please comment and let me know!
Top comments (1)
If you are in an interview and you get stuck on the ASD or System Design questions you can use this tool to solve the question for you live: ghostengineer.com