It seems that coding tests are conducted overseas in interviews with engineers, and in many cases, the main thing is to implement specific functions and classes according to the theme.
Apparently, many engineers take measures on the site called LetCode.
It is a site that trains the algorithmic power that can withstand the coding test that is being done in the early story, and it is an inevitable path for those who want to build a career at an overseas tech company.
I wrote it in a big way, but I have no plans to have such an interview at the moment.
However, as an IT engineer, it would be better to have the same level of algorithm power as a person, so I would like to solve the problem irregularly and write down the method I thought at that time as a memo.
I'm solving it with Python3.
Leet Code Table of Contents Starting from Zero
Last time Leet Code Day59 starting from zero "1221. Split a String in Balanced Strings"
Right now, I'm prioritizing the Medium of the Top 100 Liked Questions. I solved all Easy, so if you are interested, please go to the table of contents.
Twitter I'm doing it.
Articles for about 2 months have been collected. I am surprised that it has continued so far.
1481. Least Number of Unique Integers after K Removals
The difficulty level is Medium. It's a fairly new issue that was added recently.
The problem is given the array ʻarrand the integerk. The problem is, after removing k` worth of elements from the array, design an algorithm that finds the minimum number of unique integers.
It's a little confusing, so let's look at an example.
Input: arr = [5,5,4], k = 1 Output: 1 Explanation: Remove the single 4, only 5 is left.
In this example, one element is only 4 in the array. So delete 4.
Since the only remaining element is 5, 5 is returned as it is.
Input: arr = [4,3,1,1,3,3,2], k = 3 Output: 2 Explanation: Remove 4, 2 and either one of the two 1s or three 3s. 1 and 3 will be left.
It is decided to delete 4 and 2, but the remaining one deletes either 1 or 3. 1 or 3 remains, but the length of the unique number itself is 2, so it is returned.
This time, we will return an integer, and no matter how we handle the array, it will not affect the answer, so I thought it would be easier to sort it early.
If the example arr = [4,3,1,1,3,3,2], then what would you do if you sort like arr = [1,1,2,3,3,4]? It will be clear at a glance if you should delete it.
Well, if I write it quickly, the problem this time is to compare the given k with the number of elements, and if k is more than the number of elements, from k to k + Subtract the number of elements and count the number of subtractions.
And finally, subtract the number of times you subtracted from the length of the original sorted array.
However, I don't think I can honestly understand even if this is written, so let's take a look at the actual code.
import collections
class Solution:
def findLeastNumOfUniqueInts(self, arr: List[int], k: int) -> int:
sorted_counts,removed_counts = sorted(Counter(arr).items(),key=lambda x: x[1]),0
for keys,values in sorted_counts:
if k >= values:
k -= values
removed_counts += 1
return len(sorted_counts) - removed_counts
# Runtime: 496 ms, faster than 92.08% of Python3 online submissions for Least Number of Unique Integers after K Removals.
# Memory Usage: 32.9 MB, less than 33.33% of Python3 online submissions for Least Number of Unique Integers after K Removals.
In Python, there is a convenient library called Counter of collections, so it's a good idea to count each number for the time being.
In the case of Example 1, it will be as follows.
Counter({5: 2, 4: 1})
And if you sort this by the value of key, it will be as follows.
[(4, 1), (5, 2)]
By the way, if you don't write much Python, take a quick look at the sort part.
sorted_counts = sorted(Counter(arr))
# [4,5]
You may want to write, but in this case, the output will be [4,5] and the number will be exhausted, so it is NG.
In addition, although the lambda expression of Python has come out,
name=lambda argument,argument, ...:formula
You can write in the form of. However, in PEP8, it is recommended to write the lambda expression as an anonymous function in Python, so this time I will follow it.
In addition, this usage is used as an argument of sorted (), but this can be sorted based on the result by applying an arbitrary function to each element by using a lambda expression in sorted (). This is to take advantage of this property.
Of course, you can define a function with def and specify it as key, but in a situation like this time where you use it only once, this way of writing is simpler. Can write.
This time, the problem was new, and probably because there weren't many respondents, we could have created something that wasn't too bad in terms of speed.
Up to here for this time. Thank you for your hard work.
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