LeetCode 75 in Python: The Study Plan Category by Category

LeetCode 75 is LeetCode's own free study plan, which it describes as 75 essential and trending problems, best for one to three months of preparation. Its problems are shorter and newer than the classic lists, and in Python many of them collapse to a few lines. That is the risk as well as the appeal: a one-line built-in can hide the algorithm an interviewer wants to hear. This page lists the plan's 22 groups in order with the Python tools each needs, the idioms worth knowing, where Python's defaults trip you up, the problems worth repeating and a four-to-six-week schedule. For the plan itself, see our LeetCode 75 guide; for how it differs from the older community list, LeetCode 75 vs Blind 75.

The 22 groups with the Python you need

The plan has 22 easy and 53 medium problems, no hard ones and none that need Premium. Counts were read from each list's own site data on November 12, 2026. Lists are edited from time to time, so numbers can drift.

Python idioms, group by group

• Array / String: Greatest Common Divisor of Strings has no answer unless str1 + str2 == str2 + str1; if it holds, the answer is str1[:math.gcd(len(str1), len(str2))]. Reverse Words in a String is ' '.join(reversed(s.split())), because split() with no argument drops repeated and edge spaces, which split(' ') does not. String Compression must write into chars in place and return the new length.
• Two Pointers: Is Subsequence can be it = iter(t); return all(ch in it for ch in s), since each in consumes the iterator up to the match. Explain it, or write the two-index loop.
• Prefix Sum: Find the Highest Altitude is max(accumulate(gain, initial=0)); Find Pivot Index needs one sum(nums) and a running left sum.
• Hash Map / Set: Unique Number of Occurrences is len(set(cnt.values())) == len(cnt). Determine if Two Strings Are Close needs the same letter set and sorted(Counter(w1).values()) == sorted(Counter(w2).values()). Equal Row and Column Pairs counts Counter(map(tuple, grid)) and looks up each column from zip(*grid), which yields columns as tuples that match the row tuples.
• Stack and Queue: Decode String keeps a stack of (previous string, repeat count) pairs. Number of Recent Calls pops from a deque while the front is older than t - 3000. Dota2 Senate keeps two deques of indexes and re-queues each winner at index plus n.
• Trees: Leaf-Similar Trees can compare two generators built with yield from. Path Sum III keeps a Counter of prefix sums, adding the current sum before recursing and removing it after.
• Graphs: Reorder Routes stores each road in both directions with a flag for the original direction and adds the flags while walking out from city 0. Evaluate Division builds a dict of dicts of weights and multiplies along a DFS path.
• Binary Search: Successful Pairs of Spells and Potions sorts potions and calls bisect_left(potions, (success + spell - 1) // spell), keeping everything in integers. Koko Eating Bananas counts hours with (p + k - 1) // k.
• Backtracking and DP: Letter Combinations is itertools.product over the digit letters, and Unique Paths is math.comb(m + n - 2, m - 1); both are fine to mention, but write the recursion or the table when asked. Longest Common Subsequence and Edit Distance are quick top-down with @cache, then worth converting to one-row tables.
• Bits, Trie, Intervals, Monotonic Stack: Minimum Flips to Make a OR b Equal to c is ((a | b) ^ c).bit_count() + (a & b & ~c).bit_count(). Search Suggestions System can skip the trie: sort products, find i = bisect_left(products, prefix) and keep the next three words that start with the prefix. Online Stock Span stores (price, span) pairs and merges smaller prices into the span.

Where Python's defaults trip you up

• Heaps are min-heaps, and here that is what you want: all four heap problems, Kth Largest Element, Smallest Number in Infinite Set, Maximum Subsequence Score and Total Cost to Hire K Workers, need the smallest item first, so heapq works without negating values. heapq.nlargest(k, nums)[-1] solves Kth Largest, but interviewers expect a size-k heap or quickselect.
• Recursion depth: Longest ZigZag Path allows 50,000 nodes, while Python's default recursion limit is 1,000 frames. A long one-sided tree can exceed it unless the judge raises the limit, so know the iterative version or call sys.setrecursionlimit.
• Mutable default arguments: def dfs(node, path=[]) shares one list across every call. Pass the list explicitly.
• String building: collect pieces in a list and ''.join them; repeated += is only fast in some Python implementations.
• Floats where integers work: Maximum Average Subarray I wants a float, which / already returns, but binary search and counting problems should stay in integers with //.

LeetCode runs the Python3 option on Python 3.14 and makes the sortedcontainers library available, as LeetCode's help page on language environments listed it on November 12, 2026.

Problems worth repeating

These teach a technique that later lists reuse. Redo them until each takes under 15 minutes:

LeetCode 75 shares only ten problems with Blind 75, so after it, Blind 75 in Python adds 65 new problems with the same tools.

A four-to-six-week schedule

That is about three problems a day for four weeks. On a six-week plan, spread the same order at about 13 problems a week, keep one day a week for repeats and use the last week to redo every problem you failed without looking at your old code.

Turning a list into interview skill

Any list only helps if the practice transfers to problems you have not seen. These habits make the difference:

1. Time-box every attempt: about 25 minutes for a medium before you read a solution.
2. Keep a log with one line per problem: the pattern, the key idea and the complexity.
3. Redo failed problems after three days, a week and three weeks, without looking at your old code.
4. Explain your approach out loud before and while you code, as you would to an interviewer.
5. In the last two weeks, switch to unseen problems without topic labels.

The patterns most lists are built on are explained in array and string patterns and tree, graph and recursion patterns.

Where CoPilot Interview fits

Finishing a list is not the same as passing an interview: interviewers score how you explain your approach, your trade-offs and your complexity out loud. CoPilot Interview is an AI interview assistant; its free AI mock interview asks coding questions, listens to your spoken explanation and scores it out of ten with a model answer, which is the part a problem list cannot train. The free plan gives 15 minutes a day of live help in sessions of up to 15 minutes, with AI mock interviews included. Online assessments and live coding rounds usually forbid outside help, so practice now and follow your employer's rules on the day.

Disclosure: CoPilot Interview is our product, so weigh what we say about it accordingly.

Frequently asked questions

How many problems are in LeetCode 75?

75 in 22 groups: 22 easy and 53 medium, with no hard problems and none that need Premium, according to LeetCode's study-plan data on November 12, 2026.

Is Python a good language for LeetCode 75?

Yes. Built-ins such as Counter, heapq and bisect keep solutions short. Be ready to write the underlying loop when a built-in hides the algorithm.

Which Python version does LeetCode use?

Python 3.14 for the Python3 option, with the sortedcontainers library available, as LeetCode's help page listed it in November 2026.

How long does LeetCode 75 take in Python?

Four to six weeks at two or three problems a day with review. LeetCode itself suggests the plan for one to three months of preparation.