Two Pointers
双指针滑动窗口的经典写法。右指针不断往右移，移动到不能往右移动为止(具体条件根据题目而定)。当右指针到最右边以后，开始挪动左指针，释放窗口左边界。第 3 题，第 76 题，第 209 题，第 424 题，第 438 题，第 567 题，第 713 题，第 763 题，第 845 题，第 881 题，第 904 题，第 978 题，第 992 题，第 1004 题，第 1040 题，第 1052 题。
快慢指针可以查找重复数字，时间复杂度 O(n)，第 287 题。
替换字母以后，相同字母能出现连续最长的长度。第 424 题。
SUM 问题集。第 1 题，第 15 题，第 16 题，第 18 题，第 167 题，第 923 题，第 1074 题。
No.
Title
Solution
Difficulty
TimeComplexity
SpaceComplexity
Favorite
Acceptance
0003
Longest Substring Without Repeating Characters
Medium
O(n)
O(1)
❤️
31.3%
0011
Container With Most Water
Medium
O(n)
O(1)
52.2%
0015
3Sum
Medium
O(n^2)
O(n)
❤️
27.8%
0016
3Sum Closest
Medium
O(n^2)
O(1)
❤️
46.3%
0018
4Sum
Medium
O(n^3)
O(n^2)
❤️
34.7%
0019
Remove Nth Node From End of List
Medium
O(n)
O(1)
35.6%
0026
Remove Duplicates from Sorted Array
Easy
O(n)
O(1)
46.4%
0027
Remove Element
Easy
O(n)
O(1)
49.1%
0028
Implement strStr()
Easy
O(n)
O(1)
35.1%
0030
Substring with Concatenation of All Words
Hard
O(n)
O(n)
❤️
26.1%
0042
Trapping Rain Water
Hard
O(n)
O(1)
❤️
50.8%
0061
Rotate List
Medium
O(n)
O(1)
31.6%
0075
Sort Colors
Medium
O(n)
O(1)
❤️
49.0%
0076
Minimum Window Substring
Hard
O(n)
O(n)
❤️
35.8%
0080
Remove Duplicates from Sorted Array II
Medium
O(n)
O(1
45.9%
0086
Partition List
Medium
O(n)
O(1)
❤️
43.1%
0088
Merge Sorted Array
Easy
O(n)
O(1)
❤️
40.6%
0125
Valid Palindrome
Easy
O(n)
O(1)
38.0%
0141
Linked List Cycle
Easy
O(n)
O(1)
❤️
42.3%
0142
Linked List Cycle II
Medium
O(n)
O(1)
❤️
39.4%
0167
Two Sum II - Input array is sorted
Easy
O(n)
O(1)
55.4%
0209
Minimum Size Subarray Sum
Medium
O(n)
O(1)
39.2%
0234
Palindrome Linked List
Easy
O(n)
O(1)
40.3%
0283
Move Zeroes
Easy
O(n)
O(1)
58.5%
0287
Find the Duplicate Number
Medium
O(n)
O(1)
❤️
57.2%
0344
Reverse String
Easy
O(n)
O(1)
70.1%
0345
Reverse Vowels of a String
Easy
O(n)
O(1)
44.9%
0349
Intersection of Two Arrays
Easy
O(n)
O(n)
64.5%
0350
Intersection of Two Arrays II
Easy
O(n)
O(n)
51.9%
0424
Longest Repeating Character Replacement
Medium
O(n)
O(1)
48.0%
0457
Circular Array Loop
Medium
30.0%
0524
Longest Word in Dictionary through Deleting
Medium
O(n)
O(1)
48.9%
0532
K-diff Pairs in an Array
Medium
O(n)
O(n)
35.0%
0567
Permutation in String
Medium
O(n)
O(1)
❤️
44.6%
0632
Smallest Range Covering Elements from K Lists
Hard
54.0%
0713
Subarray Product Less Than K
Medium
O(n)
O(1)
40.4%
0763
Partition Labels
Medium
O(n)
O(1)
❤️
77.9%
0826
Most Profit Assigning Work
Medium
O(n log n)
O(n)
39.0%
0828
Count Unique Characters of All Substrings of a Given String
Hard
O(n)
O(1)
❤️
46.7%
0838
Push Dominoes
Medium
O(n)
O(n)
49.7%
0844
Backspace String Compare
Easy
O(n)
O(n)
46.8%
0845
Longest Mountain in Array
Medium
O(n)
O(1)
38.5%
0881
Boats to Save People
Medium
O(n log n)
O(1)
48.7%
0904
Fruit Into Baskets
Medium
O(n log n)
O(1)
42.9%
0923
3Sum With Multiplicity
Medium
O(n^2)
O(n)
36.1%
0925
Long Pressed Name
Easy
O(n)
O(1)
38.3%
0930
Binary Subarrays With Sum
Medium
O(n)
O(n)
❤️
44.3%
0977
Squares of a Sorted Array
Easy
O(n)
O(1)
72.2%
0986
Interval List Intersections
Medium
O(n)
O(1)
68.1%
0992
Subarrays with K Different Integers
Hard
O(n)
O(n)
❤️
50.5%
1004
Max Consecutive Ones III
Medium
O(n)
O(1)
60.6%
1093
Statistics from a Large Sample
Medium
O(n)
O(1)
49.4%
1234
Replace the Substring for Balanced String
Medium
34.4%
1658
Minimum Operations to Reduce X to Zero
Medium
33.4%
1695
Maximum Erasure Value
Medium
49.7%
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