Sliding Window LeetCode Problems: All 116,
With Python Solutions

Every problem in this library that LeetCode tags Sliding Window. 102 of them carry a complete Python solution, a worked example and the time and space complexity of the approach.

Get Stealth Interview

Easy: 12
Medium: 74
Hard: 30

1 pattern

How Sliding Window problems are solved

A tag names the subject, not the method. These pattern hubs cover the techniques that actually solve Sliding Window problems — each one explains the approach, gives a Python template and states its complexity.

Sliding WindowCollapse a nested loop over every subarray into a single pass with two indices.

Eyes only

When the Sliding Window problem arrives live.

In the live round, Stealth Interview reads the problem off your screen, returns a working solution with a step-by-step explanation and its time and space complexity, and transcribes what the interviewer says. It's a desktop app for macOS and Windows, invisible to screen sharing.

Get Stealth Interview See pricing

90%Subscription

python

Please analyze this context and help me answer the question or solve the problem.

Technical interview · 45 minsolution.pyShared editor · Python 3Longest substring without repeatsMediumGiven a string s, return the length of the longest contiguous substring in which every character is unique.s = "abcabcbb"
→ 31def length_of_longest_substring(s: str) -> int:2 last_seen = {}3 left = best = 04 for right, ch in enumerate(s):5 if ch in last_seen and last_seen[ch] >= left:

python

def length_of_longest_substring(s: str) -> int:    last_seen = {}                    # char -> index    left = best = 0    for right, ch in enumerate(s):        if ch in last_seen and last_seen[ch] >= left:            left = last_seen[ch] + 1  # jump past it        last_seen[ch] = right        best = max(best, right - left + 1)    return best    last_seen = {}                    # char -> index

Approach

At each index r, the window's left edge is:

left r = max (left r -1, last[s r] + 1)

Time O(n): each character enters and leaves the window once.
Space O(min(n, k)): k is the size of the character set.

Type your message...

GPT-6.1 Terra

90%Subscription

python

Please analyze this context and help me answer the question or solve the problem.

python

def length_of_longest_substring(s: str) -> int:    last_seen = {}                    # char -> index    left = best = 0    for right, ch in enumerate(s):        if ch in last_seen and last_seen[ch] >= left:            left = last_seen[ch] + 1  # jump past it        last_seen[ch] = right        best = max(best, right - left + 1)    return best    last_seen = {}                    # char -> index

Approach

At each index r, the window's left edge is:

left r = max (left r -1, last[s r] + 1)

Time O(n): each character enters and leaves the window once.
Space O(min(n, k)): k is the size of the character set.

Type your message...

GPT-6.1 TerraClear chat

QuitEscHide+QCapture+PCrop+OSubmit+EnterPress to get answerLeft/Right+Up/Down+

90%Subscription

python

Please analyze this context and help me answer the question or solve the problem.

python

def length_of_longest_substring(s: str) -> int:    last_seen = {}                    # char -> index    left = best = 0    for right, ch in enumerate(s):        if ch in last_seen and last_seen[ch] >= left:            left = last_seen[ch] + 1  # jump past it        last_seen[ch] = right        best = max(best, right - left + 1)    return best    last_seen = {}                    # char -> index

Approach

At each index r, the window's left edge is:

left r = max (left r -1, last[s r] + 1)

Time O(n): each character enters and leaves the window once.
Space O(min(n, k)): k is the size of the character set.

Type your message...

GPT-6.1 TerraClear chat

Primary display

QuitEscHide+QCapture+PCrop+OSubmit+EnterPress to get answerLeft/Right+Up/Down+

Sliding Window problems by difficulty

Problems with a complete Python solution are listed first, then by ascending problem number.

Easy (12)

Easy problems
No.	Problem	Topics
0219	Contains Duplicate II	Array, Hash Table, Sliding Window
0594	Longest Harmonious Subsequence	Array, Hash Table, Counting +2
0643	Maximum Average Subarray I	Array, Sliding Window
1652	Defuse the Bomb	Array, Sliding Window
1763	Longest Nice Substring	Bit Manipulation, Hash Table, String +2
1876	Substrings of Size Three with Distinct Characters	Hash Table, String, Counting +1
1984	Minimum Difference Between Highest and Lowest of K Scores	Array, Sorting, Sliding Window
2269	Find the K-Beauty of a Number	Math, String, Sliding Window
2379	Minimum Recolors to Get K Consecutive Black Blocks	String, Sliding Window
2760	Longest Even Odd Subarray With Threshold	Array, Sliding Window
2932	Maximum Strong Pair XOR I	Bit Manipulation, Trie, Array +2
1176	Diet Plan PerformancePremium	Array, Sliding Window

Medium (74)

Medium problems
No.	Problem	Topics
0003	Longest Substring Without Repeating Characters	Hash Table, String, Sliding Window
0187	Repeated DNA Sequences	Bit Manipulation, Hash Table, String +3
0209	Minimum Size Subarray Sum	Array, Binary Search, Prefix Sum +1
0395	Longest Substring with At Least K Repeating Characters	Hash Table, String, Divide and Conquer +1
0413	Arithmetic Slices	Array, Dynamic Programming, Sliding Window
0424	Longest Repeating Character Replacement	Hash Table, String, Sliding Window
0438	Find All Anagrams in a String	Hash Table, String, Sliding Window
0567	Permutation in String	Hash Table, Two Pointers, String +1
0658	Find K Closest Elements	Array, Two Pointers, Binary Search +3
0713	Subarray Product Less Than K	Array, Binary Search, Prefix Sum +1
0718	Maximum Length of Repeated Subarray	Array, Binary Search, Dynamic Programming +3
0837	New 21 Game	Math, Dynamic Programming, Sliding Window +1
0904	Fruit Into Baskets	Array, Hash Table, Sliding Window
0930	Binary Subarrays With Sum	Array, Hash Table, Prefix Sum +1
0978	Longest Turbulent Subarray	Array, Dynamic Programming, Sliding Window
1004	Max Consecutive Ones III	Array, Binary Search, Prefix Sum +1
1016	Binary String With Substrings Representing 1 To N	Bit Manipulation, Hash Table, String +1
1031	Maximum Sum of Two Non-Overlapping Subarrays	Array, Dynamic Programming, Sliding Window
1040	Moving Stones Until Consecutive II	Array, Math, Sorting +1
1052	Grumpy Bookstore Owner	Array, Sliding Window
1156	Swap For Longest Repeated Character Substring	Hash Table, String, Sliding Window
1208	Get Equal Substrings Within Budget	String, Binary Search, Prefix Sum +1
1234	Replace the Substring for Balanced String	String, Sliding Window
1248	Count Number of Nice Subarrays	Array, Hash Table, Math +2
1297	Maximum Number of Occurrences of a Substring	Hash Table, String, Sliding Window
1343	Number of Sub-arrays of Size K and Average Greater than or Equal to Threshold	Array, Sliding Window
1358	Number of Substrings Containing All Three Characters	Hash Table, String, Sliding Window
1423	Maximum Points You Can Obtain from Cards	Array, Prefix Sum, Sliding Window
1438	Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit	Queue, Array, Ordered Set +3
1456	Maximum Number of Vowels in a Substring of Given Length	String, Sliding Window
1477	Find Two Non-overlapping Sub-arrays Each With Target Sum	Array, Hash Table, Binary Search +2
1493	Longest Subarray of 1's After Deleting One Element	Array, Dynamic Programming, Sliding Window
1658	Minimum Operations to Reduce X to Zero	Array, Hash Table, Binary Search +2
1695	Maximum Erasure Value	Array, Hash Table, Sliding Window
1838	Frequency of the Most Frequent Element	Greedy, Array, Binary Search +3
1839	Longest Substring Of All Vowels in Order	String, Sliding Window
1871	Jump Game VII	String, Dynamic Programming, Prefix Sum +1
1888	Minimum Number of Flips to Make the Binary String Alternating	String, Dynamic Programming, Sliding Window
2024	Maximize the Confusion of an Exam	String, Binary Search, Prefix Sum +1
2090	K Radius Subarray Averages	Array, Sliding Window
2110	Number of Smooth Descent Periods of a Stock	Array, Math, Two Pointers +2
2134	Minimum Swaps to Group All 1's Together II	Array, Sliding Window
2260	Minimum Consecutive Cards to Pick Up	Array, Hash Table, Sliding Window
2271	Maximum White Tiles Covered by a Carpet	Greedy, Array, Binary Search +3
2401	Longest Nice Subarray	Bit Manipulation, Array, Sliding Window
2411	Smallest Subarrays With Maximum Bitwise OR	Bit Manipulation, Array, Binary Search +1
2461	Maximum Sum of Distinct Subarrays With Length K	Array, Hash Table, Sliding Window
2516	Take K of Each Character From Left and Right	Hash Table, String, Sliding Window
2537	Count the Number of Good Subarrays	Array, Hash Table, Sliding Window
2555	Maximize Win From Two Segments	Array, Binary Search, Sliding Window
2653	Sliding Subarray Beauty	Array, Hash Table, Sliding Window
2730	Find the Longest Semi-Repetitive Substring	String, Sliding Window
2747	Count Zero Request Servers	Array, Hash Table, Sorting +1
2762	Continuous Subarrays	Queue, Array, Ordered Set +3
2779	Maximum Beauty of an Array After Applying Operation	Array, Binary Search, Sorting +1
2799	Count Complete Subarrays in an Array	Array, Hash Table, Sliding Window
2831	Find the Longest Equal Subarray	Array, Hash Table, Binary Search +1
2841	Maximum Sum of Almost Unique Subarray	Array, Hash Table, Sliding Window
2875	Minimum Size Subarray in Infinite Array	Array, Hash Table, Prefix Sum +1
2904	Shortest and Lexicographically Smallest Beautiful String	String, Sliding Window
2958	Length of Longest Subarray With at Most K Frequency	Array, Hash Table, Sliding Window
2962	Count Subarrays Where Max Element Appears at Least K Times	Array, Sliding Window
2981	Find Longest Special Substring That Occurs Thrice I	Hash Table, String, Binary Search +2
2982	Find Longest Special Substring That Occurs Thrice II	Hash Table, String, Binary Search +2
0159	Longest Substring with At Most Two Distinct CharactersPremium	Hash Table, String, Sliding Window
0340	Longest Substring with At Most K Distinct CharactersPremium	Hash Table, String, Sliding Window
0487	Max Consecutive Ones IIPremium	Array, Dynamic Programming, Sliding Window
1100	Find K-Length Substrings With No Repeated CharactersPremium	Hash Table, String, Sliding Window
1151	Minimum Swaps to Group All 1's TogetherPremium	Array, Sliding Window
1852	Distinct Numbers in Each SubarrayPremium	Array, Hash Table, Sliding Window
1918	Kth Smallest Subarray SumPremium	Array, Binary Search, Sliding Window
2067	Number of Equal Count SubstringsPremium	Hash Table, String, Counting +1
2107	Number of Unique Flavors After Sharing K CandiesPremium	Array, Hash Table, Sliding Window
2743	Count Substrings Without Repeating CharacterPremium	Hash Table, String, Sliding Window

Hard (30)

Hard problems
No.	Problem	Topics
0030	Substring with Concatenation of All Words	Hash Table, String, Sliding Window
0076	Minimum Window Substring	Hash Table, String, Sliding Window
0220	Contains Duplicate III	Array, Bucket Sort, Ordered Set +2
0239	Sliding Window Maximum	Queue, Array, Sliding Window +2
0480	Sliding Window Median	Array, Hash Table, Sliding Window +1
0632	Smallest Range Covering Elements from K Lists	Greedy, Array, Hash Table +3
0689	Maximum Sum of 3 Non-Overlapping Subarrays	Array, Dynamic Programming, Prefix Sum +1
0862	Shortest Subarray with Sum at Least K	Queue, Array, Binary Search +4
0992	Subarrays with K Different Integers	Array, Hash Table, Counting +1
0995	Minimum Number of K Consecutive Bit Flips	Bit Manipulation, Queue, Array +2
1044	Longest Duplicate Substring	String, Binary Search, Suffix Array +3
1425	Constrained Subsequence Sum	Queue, Array, Dynamic Programming +3
1499	Max Value of Equation	Queue, Array, Sliding Window +2
1610	Maximum Number of Visible Points	Geometry, Array, Math +2
1703	Minimum Adjacent Swaps for K Consecutive Ones	Greedy, Array, Prefix Sum +1
2009	Minimum Number of Operations to Make Array Continuous	Array, Hash Table, Binary Search +1
2106	Maximum Fruits Harvested After at Most K Steps	Array, Binary Search, Prefix Sum +1
2156	Find Substring With Given Hash Value	String, Sliding Window, Hash Function +1
2302	Count Subarrays With Score Less Than K	Array, Binary Search, Prefix Sum +1
2398	Maximum Number of Robots Within Budget	Queue, Array, Binary Search +4
2444	Count Subarrays With Fixed Bounds	Queue, Array, Sliding Window +1
2528	Maximize the Minimum Powered City	Greedy, Queue, Array +3
2781	Length of the Longest Valid Substring	Array, Hash Table, String +1
2902	Count of Sub-Multisets With Bounded Sum	Array, Hash Table, Dynamic Programming +1
2935	Maximum Strong Pair XOR II	Bit Manipulation, Trie, Array +2
2953	Count Complete Substrings	Hash Table, String, Sliding Window
2968	Apply Operations to Maximize Frequency Score	Array, Binary Search, Prefix Sum +2
0683	K Empty SlotsPremium	Binary Indexed Tree, Segment Tree, Queue +5
0727	Minimum Window SubsequencePremium	String, Dynamic Programming, Sliding Window
2524	Maximum Frequency Score of a SubarrayPremium	Stack, Array, Hash Table +2

How Sliding Window problems are solved

When the Sliding Window problem arrives live.

Approach

Approach

Approach

Sliding Window problems by difficulty

Easy (12)12

Medium (74)74

Hard (30)30

Keep exploring

Easy (12)

Medium (74)

Hard (30)