String Interview Questions

Character arrays, parsing, pattern matching, and text algorithms.

268 problems

#	Title	Difficulty	Topics
5	Longest Palindromic Substring	Medium	string
6	ZigZag Conversion	Easy	string
8	String to Integer (atoi)	Easy	string
14	Longest Common Prefix	Easy	string
28	Implement strStr()	Easy	string
38	Count and Say	Easy	string
43	Multiply Strings	Medium	string
58	Length of Last Word	Easy	string
67	Add Binary	Easy	string
68	Text Justification	Hard	string
125	Valid Palindrome	Easy	string
151	Reverse Words in a String	Medium	string
161	One Edit Distance	Medium	string
165	Compare Version Numbers	Easy	string
186	Reverse Words in a String II	Medium	string
214	Shortest Palindrome	Hard	string
242	Valid Anagram	Easy	string
271	Encode and Decode Strings	Medium	string
273	Integer to English Words	Hard	string
306	Addictive Number	Medium	string
383	Ransom Note	Easy	string
405	Convert a Number to Hexadecimal	Easy	string
408	Valid Word Abbreviation	Easy	string
415	Add Strings	Easy	string
420	Strong Password Checker	Hard	string
434	Number of Segments in a String	Easy	string
443	String Compression	Easy	string
459	Repeated Substring Pattern	Easy	string
468	Validate IP Address	Medium	string
481	Magical String	Medium	string
482	License Key Formatting	Easy	string
500	Keyboard Row	Easy	string
520	Detect Capital	Easy	string
521	Longest Uncommon Subsequence I	Easy	string
522	Longest Uncommon Subsequence II	Medium	string
524	Longest Word in Dictionary through Deleting	Medium	string
527	Word Abbreviation	Hard	string
539	Minimum Time Difference	Medium	string
541	Reverse String II	Easy	string
551	Student Attendance Record I	Easy	string
555	Split Concatenated Strings	Medium	string
556	Next Greater Element III	Medium	string
557	Reverse Words in a String III	Easy	string
564	Find the Closest Palindrome	Hard	string
591	Tag Validator	Hard	string
616	Add Bold Tag in String	Medium	string
647	Palindromic Substrings	Medium	string
648	Replace Words	Medium	string
657	Robot Return to Origin	Easy	string
678	Valid Parenthesis String	Medium	string
680	Valid Palindrome II	Easy	string
681	Next Closest Time	Medium	string
686	Repeated String Match	Easy	string
696	Count Binary Substrings	Easy	string
709	To Lower Case	Easy	string
720	Longest Word in Dictionary	Easy	string
722	Remove Comments	Medium	string
751	IP to CIDR	Medium	string
758	Bold Words in String	Easy	string
791	Custom Sort String	Medium	string
796	Rotate String	Easy	string
804	Unique Morse Code Words	Easy	string
806	Number of Lines To Write String	Easy	string
809	Expressive Words	Medium	string
816	Ambiguous Coordinates	Medium	string
819	Most Common Word	Easy	string
820	Short Encoding of Words	Medium	string
824	Goat Latin	Easy	string
831	Masking Personal Information	Medium	string
833	Find And Replace in String	Medium	string
839	Similar String Groups	Hard	string
848	Shifting Letters	Medium	string
859	Buddy Strings	Easy	string
880	Decoded String at Index	Medium	string
884	Uncommon Words from Two Sentences	Easy	string
890	Find and Replace Pattern	Medium	string
893	Groups of Special-Equivalent Strings	Easy	string
916	Word Subsets	Medium	string
917	Reverse Only Letters	Easy	string
925	Long Pressed Name	Easy	string
929	Unique Email Addresses	Easy	string
939	Minimum Area Rectangle	Medium	string
942	DI String Match	Easy	string
944	Delete Columns to Make Sorted	Medium	string
953	Verifying an Alien Dictionary	Easy	string
955	Delete Columns to Make Sorted II	Medium	string
1016	Binary String With Substrings Representing 1 To N	Medium	string
1023	Camelcase Matching	Medium	string
1056	Confusing Number	Easy	string
1061	Lexicographically Smallest Equivalent String	Medium	string
1071	Greatest Common Divisor of Strings	Easy	string
1078	Occurrences After Bigram	Easy	string
1100	Find K-Length Substrings With No Repeated Characters	Medium	string
1108	Defanging an IP Address	Easy	string
1119	Remove Vowels from a String	Easy	string
1147	Longest Chunked Palindrome Decomposition	Hard	string
1177	Can Make Palindrome from Substring	Medium	string
1178	Number of Valid Words for Each Puzzle	Hard	string
1189	Maximum Number of Balloons	Easy	string
1233	Remove Sub-Folders from the Filesystem	Medium	string
1271	Hexspeak	Easy	string
1309	Decrypt String from Alphabet to Integer Mapping	Easy	string
1324	Print Words Vertically	Medium	string
1328	Break a Palindrome	Medium	string
1332	Remove Palindromic Subsequences	Easy	string
1347	Minimum Number of Steps to Make Two Strings Anagram	Medium	string
1370	Increasing Decreasing String	Easy	string
1371	Find the Longest Substring Containing Vowels in Even Counts	Medium	string
1374	Generate a String With Characters That Have Odd Count	Easy	string
1392	Longest Happy Prefix	Hard	string
1408	String Matching in an Array	Easy	string
1410	HTML Entity Parser	Medium	string
1417	Reformat The String	Easy	string
1422	Maximum Score After Splitting a String	Easy	string
1436	Destination City	Easy	string
1446	Consecutive Characters	Easy	string
1455	Check If a Word Occurs As a Prefix of Any Word in a Sentence	Easy	string
1461	Check If a String Contains All Binary Codes of Size K	Medium	string
1496	Path Crossing	Easy	string
1507	Reformat Date	Easy	string
1528	Shuffle String	Easy	string
1529	Bulb Switcher IV	Medium	string
1540	Can Convert String in K Moves	Medium	string
1542	Find Longest Awesome Substring	Hard	string
1544	Make The String Great	Easy	string
1545	Find Kth Bit in Nth Binary String	Medium	string
1554	Strings Differ by One Character	Medium	string
1556	Thousand Separator	Easy	string
1573	Number of Ways to Split a String	Medium	string
1576	Replace All ?'s to Avoid Consecutive Repeating Characters	Easy	string
1592	Rearrange Spaces Between Words	Easy	string
1598	Crawler Log Folder	Easy	string
1614	Maximum Nesting Depth of the Parentheses	Easy	string
1624	Largest Substring Between Two Equal Characters	Easy	string
1638	Count Substrings That Differ by One Character	Medium	string
1662	Check If Two String Arrays are Equivalent	Easy	string
1668	Maximum Repeating Substring	Easy	string
1678	Goal Parser Interpretation	Easy	string
1684	Count the Number of Consistent Strings	Easy	string
1694	Reformat Phone Number	Easy	string
1698	Number of Distinct Substrings in a String	Medium	string
1704	Determine if String Halves Are Alike	Easy	string
1763	Longest Nice Substring	Easy	string
1768	Merge Strings Alternately	Easy	string
1784	Check if Binary String Has at Most One Segment of Ones	Easy	string
1790	Check if One String Swap Can Make Strings Equal	Easy	string
1796	Second Largest Digit in a String	Easy	string
1805	Number of Different Integers in a String	Easy	string
1813	Sentence Similarity III	Medium	string
1816	Truncate Sentence	Easy	string
1832	Check if the Sentence Is Pangram	Easy	string
1839	Longest Substring Of All Vowels in Order	Medium	string
1844	Replace All Digits with Characters	Easy	string
1854	Maximum Population Year	Easy	string
1858	Longest Word With All Prefixes	Medium	string
1876	Substrings of Size Three with Distinct Characters	Easy	string
1880	Check if Word Equals Summation of Two Words	Easy	string
1903	Largest Odd Number in String	Easy	string
1910	Remove All Occurrences of a Substring	Medium	string
1933	Check if String Is Decomposable Into Value-Equal Substrings	Easy	string
1935	Maximum Number of Words You Can Type	Easy	string
1957	Delete Characters to Make Fancy String	Easy	string
1961	Check If String Is a Prefix of Array	Easy	string
1963	Minimum Number of Swaps to Make the String Balanced	Medium	string
1967	Number of Strings That Appear as Substrings in Word	Easy	string
1974	Minimum Time to Type Word Using Special Typewriter	Easy	string
2000	Reverse Prefix of Word	Easy	string
2042	Check if Numbers Are Ascending in a Sentence	Easy	string
2047	Number of Valid Words in a Sentence	Easy	string
2048	Next Greater Numerically Balanced Number	Medium	string
2081	Sum of k-Mirror Numbers	Hard	string
2103	Rings and Rods	Easy	string
2108	Find First Palindromic String in the Array	Easy	string
2109	Adding Spaces to a String	Medium	string
2114	Maximum Number of Words Found in Sentences	Easy	string
2116	Check if a Parentheses String Can Be Valid	Medium	string
2124	Check if All A's Appears Before All B's	Easy	string
2129	Capitalize the Title	Easy	string
2131	Longest Palindrome by Concatenating Two Letter Words	Medium	string
2135	Count Words Obtained After Adding a Letter	Medium	string
2138	Divide a String Into Groups of Size k	Easy	string
2156	Find Substring With Given Hash Value	Medium	string
2157	Groups of Strings	Hard	string
2168	Unique Substrings With Equal Digit Frequency	Medium	string
2185	Counting Words With a Given Prefix	Easy	string
2186	Minimum Number of Steps to Make Two Strings Anagram II	Medium	string
2211	Count Collisions on a Road	Medium	string
2213	Longest Substring of One Repeating Character	Hard	string
2223	Sum of Scores of Built Strings	Hard	string
2232	Minimize Result by Adding Parentheses to Expression	Medium	string
2243	Calculate Digit Sum of a String	Easy	string
2255	Count Prefixes of a Given String	Easy	string
2264	Largest 3-Same-Digit Number in String	Easy	string
2269	Find the K-Beauty of a Number	Easy	string
2272	Substring With Largest Variance	Hard	string
2273	Find Resultant Array After Removing Anagrams	Easy	string
2278	Percentage of Letter in String	Easy	string
2288	Apply Discount to Prices	Medium	string
2299	Strong Password Checker II	Easy	string
2301	Match Substring After Replacement	Hard	string
2315	Count Asterisks	Easy	string
2381	Shifting Letters II	Medium	string
2390	Removing Stars From a String	Medium	string
2414	Length of the Longest Alphabetical Continuous Substring	Medium	string
2416	Sum of Prefix Scores of Strings	Hard	string
2490	Circular Sentence	Easy	string
2496	Maximum Value of a String in an Array	Easy	string
2575	Find the Divisibility Array of a String	Medium	string
2586	Count the Number of Vowel Strings in Range	Medium	string
2678	Number of Senior Citizens	Easy	string
2710	Remove Trailing Zeros From a String	Easy	string
2729	Check if The Number is Fascinating	Easy	string
2788	Split Strings by Separator	Easy	string
2800	Shortest String That Contains Three Strings	Medium	string
2810	Faulty Keyboard	Easy	string
2828	Check if a String Is an Acronym of Words	Easy	string
2843	Count Symmetric Integers	Easy	string
2851	String Transformation	Hard	string
2937	Make Three Strings Equal	Easy	string
2942	Find Words Containing Character	Easy	string
2967	Minimum Cost to Make Array Equalindromic	Medium	string
3019	Number of Changing Keys	Easy	string
3023	Find Pattern in Infinite Stream I	Medium	string
3029	Minimum Time to Revert Word to Initial State I	Medium	string
3031	Minimum Time to Revert Word to Initial State II	Hard	string
3034	Number of Subarrays That Match a Pattern I	Medium	string
3036	Number of Subarrays That Match a Pattern II	Hard	string
3037	Find Pattern in Infinite Stream II	Hard	string
3042	Count Prefix and Suffix Pairs I	Easy	string
3043	Find the Length of the Longest Common Prefix	Medium	string
3045	Count Prefix and Suffix Pairs II	Hard	string
3076	Shortest Uncommon Substring in an Array	Medium	string
3093	Longest Common Suffix Queries	Hard	string
3110	Score of a String	Easy	string
3136	Valid Word	Easy	string
3163	String Compression III	Medium	string
3210	Find the Encrypted String	Medium	string
3271	Hash Divided String	Medium	string
3280	Convert Date to Binary	Easy	string
3303	Find the Occurrence of First Almost Equal Substring	Hard	string
3324	Find the Sequence of Strings Appeared on the Screen	Medium	string
3340	Check Balanced String	Easy	string
3407	Substring Matching Pattern	Easy	string
3455	Shortest Matching Substring	Hard	string
3456	Find Special Substring of Length K	Easy	string
3491	Phone Number Prefix	Easy	string
3498	Reverse Degree of a String	Easy	string
3529	Count Cells in Overlapping Horizontal and Vertical Substrings	Medium	string
3571	Find the Shortest Superstring II	Easy	string
3582	Generate Tag for Video Caption	Easy	string
3598	Longest Common Prefix Between Adjacent Strings After Removals	Medium	string
3606	Coupon Code Validator	Easy	string
3744	Find Kth Character in Expanded String	Medium	string
3746	Minimum String Length After Balanced Removals	Medium	string
3748	Count Stable Subarrays	Hard	string
3758	Convert Number Words to Digits	Medium	string
3775	Reverse Words With Same Vowel Count	Medium	string
3777	Minimum Deletions to Make Alternating Substring	Hard	string
3794	Reverse String Prefix	Easy	string
3813	Vowel-Consonant Score	Easy	string
3823	Reverse Letters Then Special Characters in a String	Easy	string
3838	Weighted Word Mapping	Easy	string
3856	Trim Trailing Vowels	Easy	string
3860	Unique Email Groups	Medium	string
3884	First Matching Character From Both Ends	Medium	string
3931	Check Adjacent Digit Differences	Easy	string
3941	Password Strength	Medium	string
3986	Number of Elapsed Seconds Between Two Times	Easy	string