Heap (Priority Queue) LeetCode Problems: All 163,
With Python Solutions

Every problem in this library that LeetCode tags Heap (Priority Queue). 138 of them carry a complete Python solution, a worked example and the time and space complexity of the approach.

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Easy: 13
Medium: 87
Hard: 63

1 pattern

How Heap (Priority Queue) problems are solved

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

Heap / Priority QueueKeep only the best k elements, or always pull the smallest, in log time.

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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.

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python

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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...

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

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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

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

Heap (Priority Queue) problems by difficulty

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

Easy (13)

Easy problems
No.	Problem	Topics
0506	Relative Ranks	Array, Sorting, Heap (Priority Queue)
0703	Kth Largest Element in a Stream	Tree, Design, Binary Search Tree +3
1046	Last Stone Weight	Array, Heap (Priority Queue)
1337	The K Weakest Rows in a Matrix	Array, Binary Search, Matrix +2
1464	Maximum Product of Two Elements in an Array	Array, Sorting, Heap (Priority Queue)
2099	Find Subsequence of Length K With the Largest Sum	Array, Hash Table, Sorting +1
2231	Largest Number After Digit Swaps by Parity	Sorting, Heap (Priority Queue)
2335	Minimum Amount of Time to Fill Cups	Greedy, Array, Sorting +1
2357	Make Array Zero by Subtracting Equal Amounts	Greedy, Array, Hash Table +3
2500	Delete Greatest Value in Each Row	Array, Matrix, Sorting +2
2558	Take Gifts From the Richest Pile	Array, Simulation, Heap (Priority Queue)
2974	Minimum Number Game	Array, Sorting, Simulation +1
1086	High FivePremium	Array, Hash Table, Sorting +1

Medium (87)

Medium problems
No.	Problem	Topics
0215	Kth Largest Element in an Array	Array, Divide and Conquer, Quickselect +2
0264	Ugly Number II	Hash Table, Math, Dynamic Programming +1
0347	Top K Frequent Elements	Array, Hash Table, Divide and Conquer +5
0355	Design Twitter	Design, Hash Table, Linked List +1
0373	Find K Pairs with Smallest Sums	Array, Heap (Priority Queue)
0378	Kth Smallest Element in a Sorted Matrix	Array, Binary Search, Matrix +2
0451	Sort Characters By Frequency	Hash Table, String, Bucket Sort +3
0621	Task Scheduler	Greedy, Array, Hash Table +3
0658	Find K Closest Elements	Array, Two Pointers, Binary Search +3
0659	Split Array into Consecutive Subsequences	Greedy, Array, Hash Table +1
0692	Top K Frequent Words	Trie, Array, Hash Table +5
0743	Network Delay Time	Depth-First Search, Breadth-First Search, Graph +2
0767	Reorganize String	Greedy, Hash Table, String +3
0786	K-th Smallest Prime Fraction	Array, Two Pointers, Binary Search +2
0787	Cheapest Flights Within K Stops	Depth-First Search, Breadth-First Search, Graph +3
0855	Exam Room	Design, Ordered Set, Heap (Priority Queue)
0912	Sort an Array	Array, Divide and Conquer, Bucket Sort +5
0973	K Closest Points to Origin	Geometry, Array, Math +4
1054	Distant Barcodes	Greedy, Array, Hash Table +3
1094	Car Pooling	Array, Prefix Sum, Sorting +2
1268	Search Suggestions System	Trie, Array, String +3
1338	Reduce Array Size to The Half	Greedy, Array, Hash Table +2
1353	Maximum Number of Events That Can Be Attended	Greedy, Array, Sorting +1
1405	Longest Happy String	Greedy, String, Heap (Priority Queue)
1424	Diagonal Traverse II	Array, Sorting, Heap (Priority Queue)
1438	Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit	Queue, Array, Ordered Set +3
1488	Avoid Flood in The City	Greedy, Array, Hash Table +2
1514	Path with Maximum Probability	Graph, Array, Shortest Path +1
1631	Path With Minimum Effort	Depth-First Search, Breadth-First Search, Union Find +4
1642	Furthest Building You Can Reach	Greedy, Array, Heap (Priority Queue)
1648	Sell Diminishing-Valued Colored Balls	Greedy, Array, Math +3
1686	Stone Game VI	Greedy, Array, Math +3
1696	Jump Game VI	Queue, Array, Dynamic Programming +2
1705	Maximum Number of Eaten Apples	Greedy, Array, Heap (Priority Queue)
1738	Find Kth Largest XOR Coordinate Value	Bit Manipulation, Array, Divide and Conquer +5
1753	Maximum Score From Removing Stones	Greedy, Math, Heap (Priority Queue)
1786	Number of Restricted Paths From First to Last Node	Graph, Topological Sort, Dynamic Programming +2
1792	Maximum Average Pass Ratio	Greedy, Array, Heap (Priority Queue)
1801	Number of Orders in the Backlog	Array, Simulation, Heap (Priority Queue)
1834	Single-Threaded CPU	Array, Sorting, Heap (Priority Queue)
1845	Seat Reservation Manager	Design, Heap (Priority Queue)
1878	Get Biggest Three Rhombus Sums in a Grid	Array, Math, Matrix +3
1882	Process Tasks Using Servers	Array, Heap (Priority Queue)
1942	The Number of the Smallest Unoccupied Chair	Array, Hash Table, Heap (Priority Queue)
1962	Remove Stones to Minimize the Total	Greedy, Array, Heap (Priority Queue)
1985	Find the Kth Largest Integer in the Array	Array, String, Divide and Conquer +3
2034	Stock Price Fluctuation	Design, Hash Table, Data Stream +2
2054	Two Best Non-Overlapping Events	Array, Binary Search, Dynamic Programming +2
2146	K Highest Ranked Items Within a Price Range	Breadth-First Search, Array, Matrix +2
2182	Construct String With Repeat Limit	Greedy, Hash Table, String +2
2208	Minimum Operations to Halve Array Sum	Greedy, Array, Heap (Priority Queue)
2233	Maximum Product After K Increments	Greedy, Array, Heap (Priority Queue)
2285	Maximum Total Importance of Roads	Greedy, Graph, Sorting +1
2333	Minimum Sum of Squared Difference	Greedy, Array, Binary Search +2
2336	Smallest Number in Infinite Set	Design, Hash Table, Ordered Set +1
2342	Max Sum of a Pair With Equal Sum of Digits	Array, Hash Table, Sorting +1
2343	Query Kth Smallest Trimmed Number	Array, String, Divide and Conquer +4
2349	Design a Number Container System	Design, Hash Table, Ordered Set +1
2353	Design a Food Rating System	Design, Array, Hash Table +3
2406	Divide Intervals Into Minimum Number of Groups	Greedy, Array, Two Pointers +3
2424	Longest Uploaded Prefix	Union Find, Design, Binary Indexed Tree +5
2456	Most Popular Video Creator	Array, Hash Table, String +2
2462	Total Cost to Hire K Workers	Array, Two Pointers, Simulation +1
2497	Maximum Star Sum of a Graph	Greedy, Graph, Array +2
2512	Reward Top K Students	Array, Hash Table, String +2
2530	Maximal Score After Applying K Operations	Greedy, Array, Heap (Priority Queue)
2542	Maximum Subsequence Score	Greedy, Array, Sorting +1
2593	Find Score of an Array After Marking All Elements	Array, Hash Table, Sorting +2
2611	Mice and Cheese	Greedy, Array, Sorting +1
2662	Minimum Cost of a Path With Special Roads	Graph, Array, Shortest Path +1
2679	Sum in a Matrix	Array, Matrix, Sorting +2
2762	Continuous Subarrays	Queue, Array, Ordered Set +3
2812	Find the Safest Path in a Grid	Breadth-First Search, Union Find, Array +3
2944	Minimum Number of Coins for Fruits	Queue, Array, Dynamic Programming +2
0253	Meeting Rooms IIPremium	Greedy, Array, Two Pointers +3
0505	The Maze IIPremium	Depth-First Search, Breadth-First Search, Graph +4
1057	Campus BikesPremium	Array, Sorting, Heap (Priority Queue)
1102	Path With Maximum Minimum ValuePremium	Depth-First Search, Breadth-First Search, Union Find +4
1135	Connecting Cities With Minimum CostPremium	Union Find, Graph, Minimum Spanning Tree +1
1167	Minimum Cost to Connect SticksPremium	Greedy, Array, Heap (Priority Queue)
1500	Design a File Sharing SystemPremium	Design, Hash Table, Data Stream +2
1810	Minimum Path Cost in a Hidden GridPremium	Depth-First Search, Breadth-First Search, Graph +5
2015	Average Height of Buildings in Each SegmentPremium	Greedy, Array, Sorting +1
2093	Minimum Cost to Reach City With DiscountsPremium	Graph, Shortest Path, Heap (Priority Queue)
2473	Minimum Cost to Buy ApplesPremium	Graph, Array, Shortest Path +1
2599	Make the Prefix Sum Non-negativePremium	Greedy, Array, Heap (Priority Queue)
2737	Find the Closest Marked NodePremium	Graph, Array, Shortest Path +1

Hard (63)

Hard problems
No.	Problem	Topics
0023	Merge k Sorted Lists	Linked List, Divide and Conquer, Heap (Priority Queue) +1
0218	The Skyline Problem	Binary Indexed Tree, Segment Tree, Array +5
0239	Sliding Window Maximum	Queue, Array, Sliding Window +2
0295	Find Median from Data Stream	Design, Two Pointers, Data Stream +2
0407	Trapping Rain Water II	Breadth-First Search, Array, Matrix +1
0420	Strong Password Checker	Greedy, String, Heap (Priority Queue)
0480	Sliding Window Median	Array, Hash Table, Sliding Window +1
0502	IPO	Greedy, Array, Sorting +1
0630	Course Schedule III	Greedy, Array, Sorting +1
0632	Smallest Range Covering Elements from K Lists	Greedy, Array, Hash Table +3
0675	Cut Off Trees for Golf Event	Breadth-First Search, Array, Matrix +1
0778	Swim in Rising Water	Depth-First Search, Breadth-First Search, Union Find +4
0857	Minimum Cost to Hire K Workers	Greedy, Array, Sorting +1
0862	Shortest Subarray with Sum at Least K	Queue, Array, Binary Search +4
0871	Minimum Number of Refueling Stops	Greedy, Array, Dynamic Programming +1
0882	Reachable Nodes In Subdivided Graph	Graph, Shortest Path, Heap (Priority Queue)
1172	Dinner Plate Stacks	Stack, Design, Hash Table +1
1263	Minimum Moves to Move a Box to Their Target Location	Breadth-First Search, Array, Matrix +1
1354	Construct Target Array With Multiple Sums	Array, Heap (Priority Queue)
1368	Minimum Cost to Make at Least One Valid Path in a Grid	Breadth-First Search, Graph, Array +3
1383	Maximum Performance of a Team	Greedy, Array, Sorting +1
1388	Pizza With 3n Slices	Greedy, Array, Dynamic Programming +1
1425	Constrained Subsequence Sum	Queue, Array, Dynamic Programming +3
1439	Find the Kth Smallest Sum of a Matrix With Sorted Rows	Array, Binary Search, Matrix +1
1499	Max Value of Equation	Queue, Array, Sliding Window +2
1606	Find Servers That Handled Most Number of Requests	Array, Ordered Set, Simulation +1
1675	Minimize Deviation in Array	Greedy, Array, Ordered Set +1
1687	Delivering Boxes from Storage to Ports	Segment Tree, Queue, Array +4
1776	Car Fleet II	Stack, Array, Math +2
1825	Finding MK Average	Design, Queue, Data Stream +2
1851	Minimum Interval to Include Each Query	Array, Binary Search, Sorting +2
1912	Design Movie Rental System	Design, Array, Hash Table +2
2102	Sequentially Ordinal Rank Tracker	Design, Data Stream, Ordered Set +1
2163	Minimum Difference in Sums After Removal of Elements	Array, Dynamic Programming, Heap (Priority Queue)
2290	Minimum Obstacle Removal to Reach Corner	Breadth-First Search, Graph, Array +3
2344	Minimum Deletions to Make Array Divisible	Array, Math, Number Theory +2
2386	Find the K-Sum of an Array	Array, Sorting, Heap (Priority Queue)
2398	Maximum Number of Robots Within Budget	Queue, Array, Binary Search +4
2402	Meeting Rooms III	Array, Hash Table, Sorting +2
2454	Next Greater Element IV	Stack, Array, Binary Search +3
2503	Maximum Number of Points From Grid Queries	Breadth-First Search, Union Find, Array +4
2532	Time to Cross a Bridge	Array, Simulation, Heap (Priority Queue)
2551	Put Marbles in Bags	Greedy, Array, Sorting +1
2577	Minimum Time to Visit a Cell In a Grid	Breadth-First Search, Graph, Array +3
2617	Minimum Number of Visited Cells in a Grid	Stack, Breadth-First Search, Union Find +5
2642	Design Graph With Shortest Path Calculator	Graph, Design, Shortest Path +1
2699	Modify Graph Edge Weights	Graph, Shortest Path, Heap (Priority Queue)
2813	Maximum Elegance of a K-Length Subsequence	Stack, Greedy, Array +3
2931	Maximum Spending After Buying Items	Greedy, Array, Matrix +2
2940	Find Building Where Alice and Bob Can Meet	Stack, Binary Indexed Tree, Segment Tree +4
2959	Number of Possible Sets of Closing Branches	Bit Manipulation, Graph, Enumeration +2
2973	Find Number of Coins to Place in Tree Nodes	Tree, Depth-First Search, Dynamic Programming +2
0272	Closest Binary Search Tree Value IIPremium	Stack, Tree, Depth-First Search +4
0358	Rearrange String k Distance ApartPremium	Greedy, Hash Table, String +3
0499	The Maze IIIPremium	Depth-First Search, Breadth-First Search, Graph +5
0642	Design Search Autocomplete SystemPremium	Depth-First Search, Design, Trie +4
0683	K Empty SlotsPremium	Binary Indexed Tree, Segment Tree, Queue +5
0759	Employee Free TimePremium	Array, Sorting, Line Sweep +1
1168	Optimize Water Distribution in a VillagePremium	Union Find, Graph, Minimum Spanning Tree +1
1183	Maximum Number of OnesPremium	Greedy, Math, Sorting +1
1199	Minimum Time to Build BlocksPremium	Greedy, Array, Math +1
2714	Find Shortest Path with K HopsPremium	Graph, Shortest Path, Heap (Priority Queue)
2969	Minimum Number of Coins for Fruits IIPremium	Queue, Array, Dynamic Programming +2

How Heap (Priority Queue) problems are solved

When the Heap (Priority Queue) problem arrives live.

Approach

Approach

Approach

Heap (Priority Queue) problems by difficulty

Easy (13)13

Medium (87)87

Hard (63)63

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Easy (13)

Medium (87)

Hard (63)