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

Every problem in this library that LeetCode tags Heap (Priority Queue) — 163 in total, 138 of them with a complete Python solution, a worked example and the time and space complexity of the approach.

163 problems
13 Easy
87 Medium
63 Hard

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 Queue — Keep only the best k elements, or always pull the smallest, in log time.

Heap (Priority Queue) problems by difficulty

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

Easy (13)

#	Problem	Difficulty	Topics
506	Relative Ranks	Easy	Array, Sorting, Heap (Priority Queue)
703	Kth Largest Element in a Stream	Easy	Tree, Design, Binary Search Tree +3
1046	Last Stone Weight	Easy	Array, Heap (Priority Queue)
1337	The K Weakest Rows in a Matrix	Easy	Array, Binary Search, Matrix +2
1464	Maximum Product of Two Elements in an Array	Easy	Array, Sorting, Heap (Priority Queue)
2099	Find Subsequence of Length K With the Largest Sum	Easy	Array, Hash Table, Sorting +1
2231	Largest Number After Digit Swaps by Parity	Easy	Sorting, Heap (Priority Queue)
2335	Minimum Amount of Time to Fill Cups	Easy	Greedy, Array, Sorting +1
2357	Make Array Zero by Subtracting Equal Amounts	Easy	Greedy, Array, Hash Table +3
2500	Delete Greatest Value in Each Row	Easy	Array, Matrix, Sorting +2
2558	Take Gifts From the Richest Pile	Easy	Array, Simulation, Heap (Priority Queue)
2974	Minimum Number Game	Easy	Array, Sorting, Simulation +1
1086	High FivePremium	Easy	Array, Hash Table, Sorting +1

Medium (87)

#	Problem	Difficulty	Topics
215	Kth Largest Element in an Array	Medium	Array, Divide and Conquer, Quickselect +2
264	Ugly Number II	Medium	Hash Table, Math, Dynamic Programming +1
347	Top K Frequent Elements	Medium	Array, Hash Table, Divide and Conquer +5
355	Design Twitter	Medium	Design, Hash Table, Linked List +1
373	Find K Pairs with Smallest Sums	Medium	Array, Heap (Priority Queue)
378	Kth Smallest Element in a Sorted Matrix	Medium	Array, Binary Search, Matrix +2
451	Sort Characters By Frequency	Medium	Hash Table, String, Bucket Sort +3
621	Task Scheduler	Medium	Greedy, Array, Hash Table +3
658	Find K Closest Elements	Medium	Array, Two Pointers, Binary Search +3
659	Split Array into Consecutive Subsequences	Medium	Greedy, Array, Hash Table +1
692	Top K Frequent Words	Medium	Trie, Array, Hash Table +5
743	Network Delay Time	Medium	Depth-First Search, Breadth-First Search, Graph +2
767	Reorganize String	Medium	Greedy, Hash Table, String +3
786	K-th Smallest Prime Fraction	Medium	Array, Two Pointers, Binary Search +2
787	Cheapest Flights Within K Stops	Medium	Depth-First Search, Breadth-First Search, Graph +3
855	Exam Room	Medium	Design, Ordered Set, Heap (Priority Queue)
912	Sort an Array	Medium	Array, Divide and Conquer, Bucket Sort +5
973	K Closest Points to Origin	Medium	Geometry, Array, Math +4
1054	Distant Barcodes	Medium	Greedy, Array, Hash Table +3
1094	Car Pooling	Medium	Array, Prefix Sum, Sorting +2
1268	Search Suggestions System	Medium	Trie, Array, String +3
1338	Reduce Array Size to The Half	Medium	Greedy, Array, Hash Table +2
1353	Maximum Number of Events That Can Be Attended	Medium	Greedy, Array, Sorting +1
1405	Longest Happy String	Medium	Greedy, String, Heap (Priority Queue)
1424	Diagonal Traverse II	Medium	Array, Sorting, Heap (Priority Queue)
1438	Longest Continuous Subarray With Absolute Diff Less Than or Equal to Limit	Medium	Queue, Array, Ordered Set +3
1488	Avoid Flood in The City	Medium	Greedy, Array, Hash Table +2
1514	Path with Maximum Probability	Medium	Graph, Array, Shortest Path +1
1631	Path With Minimum Effort	Medium	Depth-First Search, Breadth-First Search, Union Find +4
1642	Furthest Building You Can Reach	Medium	Greedy, Array, Heap (Priority Queue)
1648	Sell Diminishing-Valued Colored Balls	Medium	Greedy, Array, Math +3
1686	Stone Game VI	Medium	Greedy, Array, Math +3
1696	Jump Game VI	Medium	Queue, Array, Dynamic Programming +2
1705	Maximum Number of Eaten Apples	Medium	Greedy, Array, Heap (Priority Queue)
1738	Find Kth Largest XOR Coordinate Value	Medium	Bit Manipulation, Array, Divide and Conquer +5
1753	Maximum Score From Removing Stones	Medium	Greedy, Math, Heap (Priority Queue)
1786	Number of Restricted Paths From First to Last Node	Medium	Graph, Topological Sort, Dynamic Programming +2
1792	Maximum Average Pass Ratio	Medium	Greedy, Array, Heap (Priority Queue)
1801	Number of Orders in the Backlog	Medium	Array, Simulation, Heap (Priority Queue)
1834	Single-Threaded CPU	Medium	Array, Sorting, Heap (Priority Queue)
1845	Seat Reservation Manager	Medium	Design, Heap (Priority Queue)
1878	Get Biggest Three Rhombus Sums in a Grid	Medium	Array, Math, Matrix +3
1882	Process Tasks Using Servers	Medium	Array, Heap (Priority Queue)
1942	The Number of the Smallest Unoccupied Chair	Medium	Array, Hash Table, Heap (Priority Queue)
1962	Remove Stones to Minimize the Total	Medium	Greedy, Array, Heap (Priority Queue)
1985	Find the Kth Largest Integer in the Array	Medium	Array, String, Divide and Conquer +3
2034	Stock Price Fluctuation	Medium	Design, Hash Table, Data Stream +2
2054	Two Best Non-Overlapping Events	Medium	Array, Binary Search, Dynamic Programming +2
2146	K Highest Ranked Items Within a Price Range	Medium	Breadth-First Search, Array, Matrix +2
2182	Construct String With Repeat Limit	Medium	Greedy, Hash Table, String +2
2208	Minimum Operations to Halve Array Sum	Medium	Greedy, Array, Heap (Priority Queue)
2233	Maximum Product After K Increments	Medium	Greedy, Array, Heap (Priority Queue)
2285	Maximum Total Importance of Roads	Medium	Greedy, Graph, Sorting +1
2333	Minimum Sum of Squared Difference	Medium	Greedy, Array, Binary Search +2
2336	Smallest Number in Infinite Set	Medium	Design, Hash Table, Ordered Set +1
2342	Max Sum of a Pair With Equal Sum of Digits	Medium	Array, Hash Table, Sorting +1
2343	Query Kth Smallest Trimmed Number	Medium	Array, String, Divide and Conquer +4
2349	Design a Number Container System	Medium	Design, Hash Table, Ordered Set +1
2353	Design a Food Rating System	Medium	Design, Array, Hash Table +3
2406	Divide Intervals Into Minimum Number of Groups	Medium	Greedy, Array, Two Pointers +3
2424	Longest Uploaded Prefix	Medium	Union Find, Design, Binary Indexed Tree +5
2456	Most Popular Video Creator	Medium	Array, Hash Table, String +2
2462	Total Cost to Hire K Workers	Medium	Array, Two Pointers, Simulation +1
2497	Maximum Star Sum of a Graph	Medium	Greedy, Graph, Array +2
2512	Reward Top K Students	Medium	Array, Hash Table, String +2
2530	Maximal Score After Applying K Operations	Medium	Greedy, Array, Heap (Priority Queue)
2542	Maximum Subsequence Score	Medium	Greedy, Array, Sorting +1
2593	Find Score of an Array After Marking All Elements	Medium	Array, Hash Table, Sorting +2
2611	Mice and Cheese	Medium	Greedy, Array, Sorting +1
2662	Minimum Cost of a Path With Special Roads	Medium	Graph, Array, Shortest Path +1
2679	Sum in a Matrix	Medium	Array, Matrix, Sorting +2
2762	Continuous Subarrays	Medium	Queue, Array, Ordered Set +3
2812	Find the Safest Path in a Grid	Medium	Breadth-First Search, Union Find, Array +3
2944	Minimum Number of Coins for Fruits	Medium	Queue, Array, Dynamic Programming +2
253	Meeting Rooms IIPremium	Medium	Greedy, Array, Two Pointers +3
505	The Maze IIPremium	Medium	Depth-First Search, Breadth-First Search, Graph +4
1057	Campus BikesPremium	Medium	Array, Sorting, Heap (Priority Queue)
1102	Path With Maximum Minimum ValuePremium	Medium	Depth-First Search, Breadth-First Search, Union Find +4
1135	Connecting Cities With Minimum CostPremium	Medium	Union Find, Graph, Minimum Spanning Tree +1
1167	Minimum Cost to Connect SticksPremium	Medium	Greedy, Array, Heap (Priority Queue)
1500	Design a File Sharing SystemPremium	Medium	Design, Hash Table, Data Stream +2
1810	Minimum Path Cost in a Hidden GridPremium	Medium	Depth-First Search, Breadth-First Search, Graph +5
2015	Average Height of Buildings in Each SegmentPremium	Medium	Greedy, Array, Sorting +1
2093	Minimum Cost to Reach City With DiscountsPremium	Medium	Graph, Shortest Path, Heap (Priority Queue)
2473	Minimum Cost to Buy ApplesPremium	Medium	Graph, Array, Shortest Path +1
2599	Make the Prefix Sum Non-negativePremium	Medium	Greedy, Array, Heap (Priority Queue)
2737	Find the Closest Marked NodePremium	Medium	Graph, Array, Shortest Path +1

Hard (63)

#	Problem	Difficulty	Topics
23	Merge k Sorted Lists	Hard	Linked List, Divide and Conquer, Heap (Priority Queue) +1
218	The Skyline Problem	Hard	Binary Indexed Tree, Segment Tree, Array +5
239	Sliding Window Maximum	Hard	Queue, Array, Sliding Window +2
295	Find Median from Data Stream	Hard	Design, Two Pointers, Data Stream +2
407	Trapping Rain Water II	Hard	Breadth-First Search, Array, Matrix +1
420	Strong Password Checker	Hard	Greedy, String, Heap (Priority Queue)
480	Sliding Window Median	Hard	Array, Hash Table, Sliding Window +1
502	IPO	Hard	Greedy, Array, Sorting +1
630	Course Schedule III	Hard	Greedy, Array, Sorting +1
632	Smallest Range Covering Elements from K Lists	Hard	Greedy, Array, Hash Table +3
675	Cut Off Trees for Golf Event	Hard	Breadth-First Search, Array, Matrix +1
778	Swim in Rising Water	Hard	Depth-First Search, Breadth-First Search, Union Find +4
857	Minimum Cost to Hire K Workers	Hard	Greedy, Array, Sorting +1
862	Shortest Subarray with Sum at Least K	Hard	Queue, Array, Binary Search +4
871	Minimum Number of Refueling Stops	Hard	Greedy, Array, Dynamic Programming +1
882	Reachable Nodes In Subdivided Graph	Hard	Graph, Shortest Path, Heap (Priority Queue)
1172	Dinner Plate Stacks	Hard	Stack, Design, Hash Table +1
1263	Minimum Moves to Move a Box to Their Target Location	Hard	Breadth-First Search, Array, Matrix +1
1354	Construct Target Array With Multiple Sums	Hard	Array, Heap (Priority Queue)
1368	Minimum Cost to Make at Least One Valid Path in a Grid	Hard	Breadth-First Search, Graph, Array +3
1383	Maximum Performance of a Team	Hard	Greedy, Array, Sorting +1
1388	Pizza With 3n Slices	Hard	Greedy, Array, Dynamic Programming +1
1425	Constrained Subsequence Sum	Hard	Queue, Array, Dynamic Programming +3
1439	Find the Kth Smallest Sum of a Matrix With Sorted Rows	Hard	Array, Binary Search, Matrix +1
1499	Max Value of Equation	Hard	Queue, Array, Sliding Window +2
1606	Find Servers That Handled Most Number of Requests	Hard	Array, Ordered Set, Simulation +1
1675	Minimize Deviation in Array	Hard	Greedy, Array, Ordered Set +1
1687	Delivering Boxes from Storage to Ports	Hard	Segment Tree, Queue, Array +4
1776	Car Fleet II	Hard	Stack, Array, Math +2
1825	Finding MK Average	Hard	Design, Queue, Data Stream +2
1851	Minimum Interval to Include Each Query	Hard	Array, Binary Search, Sorting +2
1912	Design Movie Rental System	Hard	Design, Array, Hash Table +2
2102	Sequentially Ordinal Rank Tracker	Hard	Design, Data Stream, Ordered Set +1
2163	Minimum Difference in Sums After Removal of Elements	Hard	Array, Dynamic Programming, Heap (Priority Queue)
2290	Minimum Obstacle Removal to Reach Corner	Hard	Breadth-First Search, Graph, Array +3
2344	Minimum Deletions to Make Array Divisible	Hard	Array, Math, Number Theory +2
2386	Find the K-Sum of an Array	Hard	Array, Sorting, Heap (Priority Queue)
2398	Maximum Number of Robots Within Budget	Hard	Queue, Array, Binary Search +4
2402	Meeting Rooms III	Hard	Array, Hash Table, Sorting +2
2454	Next Greater Element IV	Hard	Stack, Array, Binary Search +3
2503	Maximum Number of Points From Grid Queries	Hard	Breadth-First Search, Union Find, Array +4
2532	Time to Cross a Bridge	Hard	Array, Simulation, Heap (Priority Queue)
2551	Put Marbles in Bags	Hard	Greedy, Array, Sorting +1
2577	Minimum Time to Visit a Cell In a Grid	Hard	Breadth-First Search, Graph, Array +3
2617	Minimum Number of Visited Cells in a Grid	Hard	Stack, Breadth-First Search, Union Find +5
2642	Design Graph With Shortest Path Calculator	Hard	Graph, Design, Shortest Path +1
2699	Modify Graph Edge Weights	Hard	Graph, Shortest Path, Heap (Priority Queue)
2813	Maximum Elegance of a K-Length Subsequence	Hard	Stack, Greedy, Array +3
2931	Maximum Spending After Buying Items	Hard	Greedy, Array, Matrix +2
2940	Find Building Where Alice and Bob Can Meet	Hard	Stack, Binary Indexed Tree, Segment Tree +4
2959	Number of Possible Sets of Closing Branches	Hard	Bit Manipulation, Graph, Enumeration +2
2973	Find Number of Coins to Place in Tree Nodes	Hard	Tree, Depth-First Search, Dynamic Programming +2
272	Closest Binary Search Tree Value IIPremium	Hard	Stack, Tree, Depth-First Search +4
358	Rearrange String k Distance ApartPremium	Hard	Greedy, Hash Table, String +3
499	The Maze IIIPremium	Hard	Depth-First Search, Breadth-First Search, Graph +5
642	Design Search Autocomplete SystemPremium	Hard	Depth-First Search, Design, Trie +4
683	K Empty SlotsPremium	Hard	Binary Indexed Tree, Segment Tree, Queue +5
759	Employee Free TimePremium	Hard	Array, Sorting, Line Sweep +1
1168	Optimize Water Distribution in a VillagePremium	Hard	Union Find, Graph, Minimum Spanning Tree +1
1183	Maximum Number of OnesPremium	Hard	Greedy, Math, Sorting +1
1199	Minimum Time to Build BlocksPremium	Hard	Greedy, Array, Math +1
2714	Find Shortest Path with K HopsPremium	Hard	Graph, Shortest Path, Heap (Priority Queue)
2969	Minimum Number of Coins for Fruits IIPremium	Hard	Queue, Array, Dynamic Programming +2

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