3Sum - Leetcode 15 - 2 Pointers (Python)

Master Data Structures & Algorithms for FREE at AlgoMap.io/
Code solutions in Python, Java, C++ and JS for this can be found at my GitHub repo here: github.com/gahogg/Leetcode-So...
Complete DSA Pathway Zero to Hero: • Data Structures & Algo...
Please check my playlists for free DSA problem solutions:
• Fundamental DSA Theory
• Array & String Questions
• 2 Pointers Questions
• Sliding Window Questions
• Binary Search Questions
• Stack Questions
• Linked List Questions
• Tree Questions
• Heap Questions
• Recursive Backtracking...
• Graph Questions
• Dynamic Programming (D...
My Data Science & ML KZbin Playlist: • Greg's Path to Become ...
Learn Python and Data Science FASTER at mlnow.ai :)
Support the content: / @greghogg
Follow me on Instagram: / greghogg5
Connect with me on LinkedIn: / greghogg
Follow me on TikTok: / greghogg5
Coursera Plus: imp.i384100.net/P0E3J6
My Favorite Courses:
Data Structures & Algorithms:
- UCalifornia San Diego DSA: imp.i384100.net/LP31oV
- Stanford Algorithms: imp.i384100.net/vNBoxd
- Python Data Structures: imp.i384100.net/NkZn47
- Meta Coding Interview Prep: imp.i384100.net/Y96rBJ
Python:
- UMichigan Python for Everybody: imp.i384100.net/QOLM73
- Python Mastery from MLNOW.ai: mlnow.ai/course-material/python/
- Google IT Automation w/ Python: imp.i384100.net/5g6Xyj
Web Dev / Full Stack:
- Meta Front-End Developer: imp.i384100.net/q4Jemy
- IBM Full Stack Developer: imp.i384100.net/Gj9dMn
- Meta Back-End Developer: imp.i384100.net/xkW0r5
- John Hopkins HTML, CSS & JS: imp.i384100.net/QyoRAA
- IBM DevOps: imp.i384100.net/kjd2r0
Cloud Development:
- AWS Fundamentals: imp.i384100.net/anqBjZ
- GCP Cloud Engineer: imp.i384100.net/g1jvqB
- Microsoft Azure Fundamentals: imp.i384100.net/EKm5O4
Game Development:
- Michigan State Unity Development: imp.i384100.net/6eOBnr
- UColorado C++ for Unreal Engine: www.coursera.org/specializati...
SQL & Data Science:
- SQL by MLNOW.ai: mlnow.ai/course-material/sql/
- Python for Data Science by MLNOW.ai: mlnow.ai/course-material/data...
- Google Data Analytics: imp.i384100.net/1rkWAR
- IBM Data Science: imp.i384100.net/P0ZRL6
- IBM Data Engineer: imp.i384100.net/4PbZyZ
Machine Learning & AI:
- ML Mastery at MLNOW.ai: mlnow.ai/course-material/ml/
- ML w/ Andrew Ng: www.coursera.org/specializati...
- Deep Learning w/ Andrew Ng: imp.i384100.net/a1kjJj

[@GregHogg]

Master Data Structures & Algorithms For FREE at AlgoMap.io!

[@abbasfadhil1715]

Naming the function three sum is wild ☠️

[@zdzisawdyrman7789]

Well... everything fine apart for the face that this solutions gets: "Time limit exceeded"

[@khndokarrashid2991]

Love your videos man! im currently a data analyst trying to transfer over to software engineering and this is helping me a lot!

[@GregHogg]

That's awesome! Glad to hear it and best of luck :)

[@jyotiaggarwal6983]

Hi, I used your solution for Python3 and after submitting,it is showing Time Limit exceeded. How can I improvise it to resolve this issue as I see we using two pointer approach here with hashMap simultaneously which costs O(N*2) complexity but sorting and storing in set increases its complexity.could you please help

[@praveenchandkakarla406]

Hi jyoti, You can use the below code without using hashmap, reference -> kzbin.info/www/bejne/oKu9pHpuo5eFb6M def threeSum(self, nums: List[int]) -> List[List[int]]: res=[] nums.sort() for i in range(len(nums)): if i>0 and nums[i] == nums[i-1]: continue l,r = i+1,len(nums)-1 while l < r: thSum = nums[i]+nums[l]+nums[r] if thSum < 0: l += 1 elif thSum > 0: r -= 1 else: res.append([nums[i],nums[l],nums[r]]) l += 1 while l < r and nums[l] == nums[l-1]: l += 1 return res

[@arindambhattacharjee9270]

@@praveenchandkakarla406 nai degi

[@praveenchandkakarla406]

@@arindambhattacharjee9270 don't need as well

[@floccinau263]

When I used this solution in Python, it was accepted. However, as you mentioned, using Python 3 causes a time limit exceed.

[@ankitchoudhary4618]

Very informative 👍

[@siddheshdewalekar7364]

Nice info👍

[@newbiedb]

At 5:21, can you explain more about hashable and mutable in Set?

[@DariusD0815]

What is considered a "duplicate triplet"? All value permutations of a triplet are duplicates? e.g. [2,-1,-1] or [-1,2,-1]?

[@GregHogg]

Yeah different permutations of the same numbers are not desired

[@SashoSuper]

I like those videos.

[@GregHogg]

Awesome!

[@NitinKumar-qs9tw]

Hey Greg! unfortunately time limit exceeded for last test case [0,0,0,0,0.........0,0,0] on Leetcode. 312/313 test cases passed.

[@GregHogg]

Yeah, they added this test case in literally a few days after I posted this video. I'll have to redo it with the n^2 solution that avoids using a Hashmap

[@samspeaks-hk1vp]

shouldn’t time complexity more than o(n3) cause we sorting in the inner loop?

[@haythemkhiari1089]

i think it is O(n^2 log(n) ) because sorting take O(log(n)) not o(n)

[@ThsHunt]

why do the step of filling hashset doesnt count towards the time

[@sonicrushXII]

It does take time, But it's constant time Constants are generally dropped when Calculating end time

[@lakshayjain9337]

Great logic But why this c++ code is storing similar strings vector threeSum(vector& nums) { unordered_map map; int i,j,n=nums.size(); vector ans; sort(nums.begin(),nums.end()); for(i=0;i

[@onlywrestling7810]

It gives TLE, only 312/313 test cases are passed

[@GregHogg]

Yes, sorry. Leetcode recently added a case to make this solution not work. At some point I'll make a solution for a different algorithm that works

[@benravenhill484]

My brain exploded

[@GregHogg]

😂

[@rakeshande449]

It's getting TLE

[@GregHogg]

Yes, they actually changed it very recently and this no longer passes! You need to do the one where you sort and then use two pointers now

[@maestro.a]

thanks for answered. I got TLE too.@@GregHogg

[@jagrat12354]

getting Time Limit Exceeded using this method, dont know why. Even running ur code does the same

[@GregHogg]

They recently changed this question so this solution doesn't run on the last test case. Very dumb of them to do that

[@saaddude1]

@@GregHogg Any idea, how to tweak the solution to pass all test cases?

[@santanu_barua]

Java Solution for this: ------------------------------------- public List threeSum(int[] nums) { Map map = new HashMap(); for (int i = 0; i< nums.length; i++) { map.put(nums[i], i); } Set result = new HashSet(); for (int i = 0; i< nums.length;i++) { for (int j = i+1; j< nums.length; j++) { int desired = -nums[i] - nums[j]; if (map.containsKey(desired) && map.get(desired)!= i && map.get(desired)!=j) { List triplet = Arrays.asList(nums[i], nums[j], desired); Collections.sort(triplet); result.add(triplet); } } } return new ArrayList(result); }

[@antipainK]

Using a set feels like cheating here...