Let Code Day 60 starting from zero "1481. Least Number of Unique Integers after K Removals"

Overview

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.

Leetcode

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.

problem

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.

solution

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.

Recommended Posts

Let Code Day 60 starting from zero "1481. Least Number of Unique Integers after K Removals"
Let Code Day87 Starting from Zero "1512. Number of Good Pairs"
Let Code Day49 starting from zero "1323. Maximum 69 Number"
Let Code Day89 "62. Unique Paths" Starting from Zero
Let Code Day14 starting from zero "136. Single Number"
Let Code Day6 Starting from Zero "1342. Number of Steps to Reduce a Number to Zero"
Let Code Day10 Starting from Zero "1431. Kids With the Greatest Number of Candies"
Let Code Day 44 "543. Diameter of Binary Tree" starting from zero
Let Code Day 64 starting from zero "287. Find the Duplicate Number"
Let Code Day81 "347. Top K Frequent Elements" Starting from Zero
Let Code Day56 Starting from Zero "5453. Running Sum of 1d Array"
Let Code Day7 starting from zero "104. Maximum Depth of Binary Tree"
Let Code Day92 Starting from Zero "4. Median of Two Sorted Arrays"
Let Code Day 35 "160. Intersection of Two Linked Lists" Starting from Zero
Let Code Day72 Starting from Zero "1498. Number of Subsequences That Satisfy the Given Sum Condition"
Let Code Day58 Starting from Zero "20. Valid Parentheses"
Let Code Day16 Starting from Zero "344. Reverse String"
Let Code Table of Contents Starting from Zero
Let Code Day18 starting from zero "53. Maximum Subarray"
Let Code Day 13 "338. Counting Bits" Starting from Zero
Let Code Day71 Starting from Zero "1496. Path Crossing"
Let Code Day 61 "7. Reverse Integer" starting from zero
Let Code Day 82 "392. Is Subsequence" Starting from Zero
Let Code Day51 Starting from Zero "647. Palindromic Substrings"
Let Code Day 50 "739. Daily Temperatures" Starting from Zero
Let Code Day 15 "283. Move Zeroes" starting from zero
Let Code Day 11 Starting from Zero "1315. Sum of Nodes with Even-Valued Grandparent"
Let Code Day74 starting from zero "12. Integer to Roman"
Let Code Day 42 "2. Add Two Numbers" Starting from Zero
Let Code Day57 Starting from Zero "35. Search Insert Position"
Let Code Day47 Starting from Zero "14. Longest Common Prefix"
Let Code Day78 Starting from Zero "206. Reverse Linked List"
Let Code Day 84 starting from zero "142. Linked List Cycle II"
Let Code Day24 Starting from Zero "21. Merge Two Sorted Lists"
Let Code Day2 Starting from Zero "1108. Defanging an IP Address"
Let Code Day70 Starting from Zero "295. Find Median from Data Stream"
Let Code Day 65 "560. Subarray Sum Equals K" starting from scratch
Let Code Day4 starting from scratch "938. Range Sum of BST"
Let Code Day48 Starting from Zero "26. Remove Duplicates from Sorted Array"
Let Code Day53 Starting from Zero "1365. How Many Numbers Are Smaller Than the Current Number"
Let Code Day67 Starting from Zero "1486. XOR Operation in an Array"
Let Code Day86 Starting from Zero "33. Search in Rotated Sorted Array"
Let Code Day5 starting from zero "1266. Minimum Time Visiting All Points"
Let Code Day83 Starting from Zero "102. Binary Tree Level Order Traversal"
Let Code Day75 starting from scratch "15.3 Sum"
Let Code Day 29 "46. Permutations" starting from scratch
Let Code Day45 Starting from Zero "1379. Find a Corresponding Node of a Binary Tree in a Clone of That Tree"
Let Code Day 40 Starting from Zero "114. Flatten Binary Tree to Linked List"
Let Code Day 91 "153. Find Minimum in Rotated Sorted Array" starting from zero
Let Code Day59 starting from zero "1221. Split a String in Balanced Strings"
Let Code Day 27 "101. Symmetric Tree" starting from scratch
Let Code Day 25 "70. Climbing Stairs" starting from scratch
Let Code Day69 starting from scratch "279. Perfect Squares"
Let Code Day 34 starting from scratch "118. Pascal's Triangle"
Let Code Day85 starting from scratch "6. ZigZag Conversion"
Let Code Day20 starting from scratch "134. Gas Station"
Let Code Day 88 "139. Word Break" starting from scratch
Let Code Day 28 "198. House Robber" starting from scratch
Let Code Day 39 "494. Target Sum" starting from scratch
Let Code Day 36 "155. Min Stack" starting from scratch
Let Code Day 17 "169. Majority Element" starting from scratch