Practice Problems

Problem of the Day: Integer Square Root — keep your streak alive!

Practice Problems — strings

#ProblemTopicsDifficulty
318 Valid Username implementation strings 1000
353 Mask the Email strings 1000
444 Evening the Counts strings 1000
70 Palindrome, Roughly strings 1100
73 Is It a Subsequence strings two-pointers 1100
76 Longest Common Prefix strings 1100
390 Longest Common Suffix strings 1100
442 Rearrange into a Palindrome strings 1100
74 Rotation of Each Other strings 1200
75 Three Kinds of Brackets strings stack 1200
90 Flips to Alternate strings greedy 1200
91 Fair Binary Split strings prefix-sums 1200
286 Look and Say implementation strings 1200
297 Binary Addition math strings 1200
319 Valid IPv4 Address implementation strings 1200
387 Reverse Every Other Chunk strings 1200
423 Balanced Prefix strings prefix-sums 1200
443 Deletions to Anagrams strings 1200
445 Favourite Bigram strings 1200
493 Parse the Number implementation strings 1200
59 Collapse Adjacent Pairs strings stack 1300
78 Count Pattern Occurrences strings 1300
422 Zero Then One math strings 1300
458 Canonical Palindrome strings 1300
77 Lexicographically Smallest Rotation strings 1400
79 Longest Substring Without Repeats strings two-pointers 1400
80 Longest Palindromic Substring strings 1500
81 Count Palindromic Substrings strings 1500
208 Decode the Message strings dp 1500
341 Anagram Windows strings sliding-window 1500
496 Longest Border strings 1500
603 All the Borders strings kmp 1500
82 Smallest Period strings 1600
216 Longest Common Subsequence strings dp 1600
342 Longest Common Substring strings dp 1600
217 Edit Distance strings dp 1700
218 Longest Palindromic Subsequence strings dp 1700
222 Shuffled Together strings dp 1700
594 How Often Each Prefix Appears strings kmp 1700
644 Sentence Reconstructions strings dp 1700
987 Minimum Insertions to Palindrome strings dp interval-dp 1700
221 Counting Embeddings strings dp 1800
639 Fewest Palindrome Cuts strings dp 1900
597 The Longest Palindrome, Fast strings manacher 2000
598 Longest Common Extension strings binary-search hashing 2000
671 Wildcard Matching strings dp 2000
591 Longest Repeat strings suffix-array 2100
596 Every Palindrome, Counted strings manacher 2100
600 Dictionary Match Count strings aho-corasick 2200
602 Rank Among the Suffixes strings suffix-array 2200