3 |
Longest Substring Without Repeating Characters |
Medium |
Hash Table |
Two Pointers
|
String
|
Sliding Window
|
5 |
Longest Palindromic Substring |
Medium |
Dynamic Programming
|
String
|
6 |
ZigZag Conversion |
Medium |
String
|
8 |
String to Integer (atoi) |
Medium |
Math
|
String
|
10 |
Regular Expression Matching |
Hard |
String
|
Dynamic Programming
|
Backtracking
|
12 |
Integer to Roman |
Medium |
Math
|
String
|
13 |
Roman to Integer |
Easy |
Math
|
String
|
14 |
Longest Common Prefix |
Easy |
String
|
17 |
Letter Combinations of a Phone Number |
Medium |
String
|
Backtracking |
Depth-first search |
Recursion
|
20 |
Valid Parentheses |
Easy |
String
|
Stack
|
22 |
Generate Parentheses |
Medium |
String
|
Backtracking
|
28 |
Implement strStr() |
Easy |
Two Pointers
|
String
|
30 |
Substring with Concatenation of All Words |
Hard |
Hash Table |
Two Pointers
|
String
|
32 |
Longest Valid Parentheses |
Hard |
String
|
Dynamic Programming
|
38 |
Count and Say |
Medium |
String
|
43 |
Multiply Strings |
Medium |
Math
|
String
|
44 |
Wildcard Matching |
Hard |
String
|
Dynamic Programming
|
Backtracking |
Greedy
|
58 |
Length of Last Word |
Easy |
String
|
126 |
Word Ladder II |
Hard |
Array
|
String
|
Backtracking |
Breadth-first Search
|
536 |
Construct Binary Tree from String |
Medium |
String
|
Tree
|
606 |
Construct String from Binary Tree |
Easy |
String
|
Tree
|
1268 |
Search Suggestions System |
Medium |
String
|
1297 |
Maximum Number of Occurrences of a Substring |
Medium |
String
|
Bit Manipulation
|
1332 |
Remove Palindromic Subsequences |
Easy |
String
|
1347 |
Minimum Number of Steps to Make Two Strings Anagram |
Medium |
String
|
1374 |
Generate a String With Characters That Have Odd Counts |
Easy |
String
|
1736 |
Latest Time by Replacing Hidden Digits |
Easy |
String
|
Greedy
|
1737 |
Change Minimum Characters to Satisfy One of Three Conditions |
Medium |
String
|
Greedy
|
1759 |
Count Number of Homogenous Substrings |
Medium |
String
|
Greedy
|
1763 |
Longest Nice Substring |
Easy |
String
|
1768 |
Merge Strings Alternately |
Easy |
String
|