Coding interview problems

3,736 problems: 937 Easy, 1,914 Medium, 885 Hard. Each runs against hidden tests, in 13 languages; database problems in SQL. Free for members.

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Problems 401–500 of 3,736

401. Dense Score Ranks Easy · Array, Hash Table, Sorting
402. Longest Neighbor-Value Selection Easy · Array, Hash Table, Counting
403. Decode with a Key Phrase Easy · String, Hash Table
404. Pair Up Equal Values Easy · Array, Hash Table, Counting, Bit Manipulation
405. Copies of a Word from Letters Easy · String, Hash Table, Counting
406. Top Word Not Banned Easy · String, Hash Table, Counting
407. Present in At Least Two Lists Easy · Array, Hash Table
408. Isolated Values Easy · Array, Hash Table, Counting
409. Letters in Every Word Easy · Array, String, Hash Table, Counting
410. Distinct Encodings Easy · Array, String, Hash Table
411. Equalize by One Removal Easy · String, Hash Table, Counting
412. Drop Repeated Nodes Easy · Linked List, Hash Table
413. Pair Sum in a Search Tree Easy · Tree, Binary Tree, Binary Search Tree, Hash Table, Depth-First Search
414. Most Common Values in a Tree Easy · Tree, Binary Tree, Hash Table, Depth-First Search, Counting
415. Score a Code Guess Easy · String, Hash Table, Counting
416. Widest Same-Letter Gap Easy · String, Hash Table
417. Busiest Grid Line Easy · Array, Hash Table, Counting
418. Values with Reversed Twins Easy · Array, Hash Table, Math
419. Equal-Value Groups Easy · Array, Hash Table, Math, Counting
420. The Trusted Host Easy · Array, Hash Table, Graph, Counting
421. Longest Palindrome from Tiles Easy · String, Hash Table, Greedy, Counting
422. Shortest Covering Word Easy · Array, String, Hash Table, Counting
423. Largest Digit-Sum Groups Easy · Hash Table, Math, Counting
424. One Swap Away Easy · String, Hash Table
425. Matching Tile Pairs Easy · Array, Hash Table, Counting
426. Pairs at a Fixed Distance Easy · Array, Hash Table, Counting
427. Evenly Spaced Triples Easy · Array, Hash Table
428. Prefix and Suffix Variety Gap Easy · Array, Hash Table
429. Odd One Out by Letter Gaps Easy · Array, String, Hash Table
430. Longest Uniform Run Seen Three Times Medium · String, Hash Table, Counting
431. Self-Describing Digits Easy · String, Hash Table, Counting
432. Longest Equal Run After Deletions Medium · Array, Hash Table, Sliding Window
433. Build a Chained Bucket Map Easy · Array, Hash Table, Design, Linked List
434. Echo Nodes in a Tree Medium · Tree, Binary Tree, Hash Table, Depth-First Search
435. Rearrangeable Palindrome Paths Medium · Tree, Binary Tree, Bit Manipulation, Depth-First Search, Hash Table
436. Commonest Subtree Totals Medium · Tree, Binary Tree, Hash Table, Depth-First Search, Counting
437. Combination Lock Escape Medium · Array, String, Hash Table, Breadth-First Search
438. Sort by Letter Frequency Medium · String, Hash Table, Sorting, Counting
439. Make Letter Counts Close Medium · String, Hash Table, Greedy, Sorting
440. Longest Stretch Without Repeats Medium · String, Hash Table, Sliding Window
441. Exact-Count Substrings Medium · String, Hash Table, Sliding Window
442. Longest Run Using at Most K Colors Medium · Array, Hash Table, Sliding Window
443. Distinct Subarrays with Few Multiples Medium · Array, Hash Table
444. Scrambled Word Hidden in Text Medium · String, Hash Table, Sliding Window
445. One-Swap Number Twins Medium · Array, Hash Table, String
446. Subarrays with Sum Divisible by K Medium · Array, Hash Table, Prefix Sum
447. Longest Subarray Summing to K Medium · Array, Hash Table, Prefix Sum
448. Longest Strong Stretch Medium · Array, Hash Table, Prefix Sum, Stack
449. Matching Row and Column Pairs Medium · Array, Hash Table, Matrix
450. Least-Recent Eviction Cache Medium · Hash Table, Linked List, Design
451. Versioned Value Store Medium · Hash Table, Binary Search, Design, String
452. Snapshot Ledger Medium · Array, Hash Table, Binary Search, Design
453. Trip Time Averages Medium · Hash Table, String, Design
454. Message Rate Limiter Medium · Array, String, Hash Table, Design
455. Fewest Bricks Cut Medium · Array, Hash Table, Counting, Prefix Sum
456. Equidistant Point Triples Medium · Array, Hash Table, Math
457. Longest Fixed-Step Chain Medium · Array, Hash Table, Dynamic Programming
458. Longest Evenly Stepped Subsequence Medium · Array, Hash Table, Dynamic Programming
459. Longest Self-Summing Subsequence Medium · Array, Hash Table, Dynamic Programming
460. Repeated Subtree Shapes Medium · Tree, Binary Tree, Hash Table, Depth-First Search
461. Downward Path Sums Medium · Tree, Binary Tree, Hash Table, Prefix Sum, Depth-First Search
462. Tree Columns Top to Bottom Medium · Tree, Binary Tree, Hash Table, Breadth-First Search, Sorting
463. Drop Zero-Sum Runs Medium · Linked List, Hash Table, Prefix Sum
464. Linked Groups of Picked Values Medium · Linked List, Hash Table
465. Split Cards into Consecutive Runs Medium · Array, Hash Table, Sorting, Greedy
466. Longest Repeated Snippet Hard · String, Hash Table, Binary Search
467. Pair Every Value with Its Double Medium · Array, Hash Table, Sorting, Greedy
468. Edits to Make an Anagram Medium · String, Hash Table, Counting
469. Universal Words Medium · Array, String, Hash Table, Counting
470. Group by Letter Shift Medium · Array, String, Hash Table
471. Even and Odd Swap Classes Medium · Array, String, Hash Table, Sorting
472. Repeated Gene Fragments Medium · String, Hash Table, Sliding Window
473. Counter with Constant-Time Extremes Hard · Hash Table, Design, Linked List
474. Longest Even-Vowel Stretch Medium · String, Hash Table, Bit Manipulation, Prefix Sum
475. Pop the Most Popular Hard · Hash Table, Stack, Design
476. Near-Palindromic Substrings Medium · String, Hash Table, Bit Manipulation, Prefix Sum
477. Windows Centered on K Hard · Array, Hash Table, Prefix Sum
478. Balanced Tri-Color Subarrays Medium · Array, Hash Table, Prefix Sum
479. Longest Shared Route Hard · Array, Hash Table, Binary Search
480. Shortest Cut for Divisibility Medium · Array, Hash Table, Prefix Sum, Math
481. First Substring with a Given Fingerprint Hard · String, Hash Table, Sliding Window
482. Pairs with a Target XOR Medium · Array, Hash Table, Bit Manipulation
483. Prefix Score Totals Hard · Array, String, Hash Table, Trie
484. Subarrays XOR-ing to K Medium · Array, Hash Table, Bit Manipulation, Prefix Sum
485. Islands up to Symmetry Hard · Array, Hash Table, Matrix, Depth-First Search
486. Best Distinct Window Sum Medium · Array, Hash Table, Sliding Window
487. Sum of Solo-Letter Counts Hard · String, Hash Table, Dynamic Programming
488. Longest Uniform Run After Edits Medium · String, Hash Table, Sliding Window
489. Count Arithmetic Subsequences Hard · Array, Hash Table, Dynamic Programming
490. Number Grid Consistency Medium · Array, Hash Table, Matrix
491. Balanced Vowel Substrings, Divisible Hard · String, Hash Table, Prefix Sum, Math
492. Distinct Island Shapes Medium · Array, Hash Table, Matrix, Depth-First Search
493. Nearby Close Values Hard · Array, Hash Table, Sliding Window
494. Equal Product Quadruples Medium · Array, Hash Table, Counting
495. Mirrored Balance Pairs Medium · Array, Hash Table, Math, Counting
496. Same-Shape Frame Pairs Medium · Array, Hash Table, Math, Counting
497. Fewest Rounds of Chores Medium · Array, Hash Table, Greedy, Counting
498. Deletions for Unique Counts Medium · String, Hash Table, Greedy, Sorting
499. Fewest Repeat-Free Pieces Medium · String, Hash Table, Greedy
500. Chunks by Last Sighting Medium · String, Hash Table, Greedy, Two Pointers