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83 lines
7.4 KiB
Markdown
83 lines
7.4 KiB
Markdown
---
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title: Two Pointers
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type: docs
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---
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# Two Pointers
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- 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。
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```c
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left, right := 0, -1
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for left < len(s) {
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if right+1 < len(s) && freq[s[right+1]-'a'] == 0 {
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freq[s[right+1]-'a']++
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right++
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} else {
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freq[s[left]-'a']--
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left++
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}
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result = max(result, right-left+1)
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}
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```
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- 快慢指针可以查找重复数字，时间复杂度 O(n)，第 287 题。
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- 替换字母以后，相同字母能出现连续最长的长度。第 424 题。
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- 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。
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| Title | Solution | Difficulty | Time | Space |收藏|
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| ----- | :--------: | :----------: | :----: | :-----: | :-----: |
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|3. Longest Substring Without Repeating Characters | [Go]({{< relref "/ChapterFour/0003.Longest-Substring-Without-Repeating-Characters.md" >}})| Medium | O(n)| O(1)|❤️|
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|11. Container With Most Water | [Go]({{< relref "/ChapterFour/0011.Container-With-Most-Water.md" >}})| Medium | O(n)| O(1)||
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|15. 3Sum | [Go]({{< relref "/ChapterFour/0015.3Sum.md" >}})| Medium | O(n^2)| O(n)|❤️|
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|16. 3Sum Closest | [Go]({{< relref "/ChapterFour/0016.3Sum-Closest.md" >}})| Medium | O(n^2)| O(1)|❤️|
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|18. 4Sum | [Go]({{< relref "/ChapterFour/0018.4Sum.md" >}})| Medium | O(n^3)| O(n^2)|❤️|
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|19. Remove Nth Node From End of List | [Go]({{< relref "/ChapterFour/0019.Remove-Nth-Node-From-End-of-List.md" >}})| Medium | O(n)| O(1)||
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|26. Remove Duplicates from Sorted Array | [Go]({{< relref "/ChapterFour/0026.Remove-Duplicates-from-Sorted-Array.md" >}})| Easy | O(n)| O(1)||
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|27. Remove Element | [Go]({{< relref "/ChapterFour/0027.Remove-Element.md" >}})| Easy | O(n)| O(1)||
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|28. Implement strStr() | [Go]({{< relref "/ChapterFour/0028.Implement-strStr.md" >}})| Easy | O(n)| O(1)||
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|30. Substring with Concatenation of All Words | [Go]({{< relref "/ChapterFour/0030.Substring-with-Concatenation-of-All-Words.md" >}})| Hard | O(n)| O(n)|❤️|
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|42. Trapping Rain Water | [Go]({{< relref "/ChapterFour/0042.Trapping-Rain-Water.md" >}})| Hard | O(n)| O(1)|❤️|
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|61. Rotate List | [Go]({{< relref "/ChapterFour/0061.Rotate-List.md" >}})| Medium | O(n)| O(1)||
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|75. Sort Colors | [Go]({{< relref "/ChapterFour/0075.Sort-Colors.md" >}})| Medium| O(n)| O(1)|❤️|
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|76. Minimum Window Substring | [Go]({{< relref "/ChapterFour/0076.Minimum-Window-Substring.md" >}})| Hard | O(n)| O(n)|❤️|
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|80. Remove Duplicates from Sorted Array II | [Go]({{< relref "/ChapterFour/0080.Remove-Duplicates-from-Sorted-Array-II.md" >}})| Medium | O(n)| O(1||
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|86. Partition List | [Go]({{< relref "/ChapterFour/0086.Partition-List.md" >}})| Medium | O(n)| O(1)|❤️|
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|88. Merge Sorted Array | [Go]({{< relref "/ChapterFour/0088.Merge-Sorted-Array.md" >}})| Easy | O(n)| O(1)|❤️|
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|125. Valid Palindrome | [Go]({{< relref "/ChapterFour/0125.Valid-Palindrome.md" >}})| Easy | O(n)| O(1)||
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|141. Linked List Cycle | [Go]({{< relref "/ChapterFour/0141.Linked-List-Cycle.md" >}})| Easy | O(n)| O(1)|❤️|
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|142. Linked List Cycle II | [Go]({{< relref "/ChapterFour/0142.Linked-List-Cycle-II.md" >}})| Medium | O(n)| O(1)|❤️|
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|167. Two Sum II - Input array is sorted | [Go]({{< relref "/ChapterFour/0167.Two-Sum-II---Input-array-is-sorted.md" >}})| Easy | O(n)| O(1)||
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|209. Minimum Size Subarray Sum | [Go]({{< relref "/ChapterFour/0209.Minimum-Size-Subarray-Sum.md" >}})| Medium | O(n)| O(1)||
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|234. Palindrome Linked List | [Go]({{< relref "/ChapterFour/0234.Palindrome-Linked-List.md" >}})| Easy | O(n)| O(1)||
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|283. Move Zeroes | [Go]({{< relref "/ChapterFour/0283.Move-Zeroes.md" >}})| Easy | O(n)| O(1)||
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|287. Find the Duplicate Number | [Go]({{< relref "/ChapterFour/0287.Find-the-Duplicate-Number.md" >}})| Easy | O(n)| O(1)|❤️|
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|344. Reverse String | [Go]({{< relref "/ChapterFour/0344.Reverse-String.md" >}})| Easy | O(n)| O(1)||
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|345. Reverse Vowels of a String | [Go]({{< relref "/ChapterFour/0345.Reverse-Vowels-of-a-String.md" >}})| Easy | O(n)| O(1)||
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|349. Intersection of Two Arrays | [Go]({{< relref "/ChapterFour/0349.Intersection-of-Two-Arrays.md" >}})| Easy | O(n)| O(n) ||
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|350. Intersection of Two Arrays II | [Go]({{< relref "/ChapterFour/0350.Intersection-of-Two-Arrays-II.md" >}})| Easy | O(n)| O(n) ||
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|424. Longest Repeating Character Replacement | [Go]({{< relref "/ChapterFour/0424.Longest-Repeating-Character-Replacement.md" >}})| Medium | O(n)| O(1) ||
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|524. Longest Word in Dictionary through Deleting | [Go]({{< relref "/ChapterFour/0524.Longest-Word-in-Dictionary-through-Deleting.md" >}})| Medium | O(n)| O(1) ||
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|532. K-diff Pairs in an Array | [Go]({{< relref "/ChapterFour/0532.K-diff-Pairs-in-an-Array.md" >}})| Easy | O(n)| O(n)||
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|567. Permutation in String | [Go]({{< relref "/ChapterFour/0567.Permutation-in-String.md" >}})| Medium | O(n)| O(1)|❤️|
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|713. Subarray Product Less Than K | [Go]({{< relref "/ChapterFour/0713.Subarray-Product-Less-Than-K.md" >}})| Medium | O(n)| O(1)||
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|763. Partition Labels | [Go]({{< relref "/ChapterFour/0763.Partition-Labels.md" >}})| Medium | O(n)| O(1)|❤️|
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|826. Most Profit Assigning Work | [Go]({{< relref "/ChapterFour/0826.Most-Profit-Assigning-Work.md" >}})| Medium | O(n log n)| O(n)||
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|828. Unique Letter String | [Go]({{< relref "/ChapterFour/0828.COPYRIGHT-PROBLEM-XXX.md" >}})| Hard | O(n)| O(1)|❤️|
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|838. Push Dominoes | [Go]({{< relref "/ChapterFour/0838.Push-Dominoes.md" >}})| Medium | O(n)| O(n)||
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|844. Backspace String Compare | [Go]({{< relref "/ChapterFour/0844.Backspace-String-Compare.md" >}})| Easy | O(n)| O(n) ||
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|845. Longest Mountain in Array | [Go]({{< relref "/ChapterFour/0845.Longest-Mountain-in-Array.md" >}})| Medium | O(n)| O(1) ||
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|881. Boats to Save People | [Go]({{< relref "/ChapterFour/0881.Boats-to-Save-People.md" >}})| Medium | O(n log n)| O(1) ||
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|904. Fruit Into Baskets | [Go]({{< relref "/ChapterFour/0904.Fruit-Into-Baskets.md" >}})| Medium | O(n log n)| O(1) ||
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|923. 3Sum With Multiplicity | [Go]({{< relref "/ChapterFour/0923.3Sum-With-Multiplicity.md" >}})| Medium | O(n^2)| O(n) ||
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|925. Long Pressed Name | [Go]({{< relref "/ChapterFour/0925.Long-Pressed-Name.md" >}})| Easy | O(n)| O(1)||
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|930. Binary Subarrays With Sum | [Go]({{< relref "/ChapterFour/0930.Binary-Subarrays-With-Sum.md" >}})| Medium | O(n)| O(n) |❤️|
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|977. Squares of a Sorted Array | [Go]({{< relref "/ChapterFour/0977.Squares-of-a-Sorted-Array.md" >}})| Easy | O(n)| O(1)||
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|986. Interval List Intersections | [Go]({{< relref "/ChapterFour/0986.Interval-List-Intersections.md" >}})| Medium | O(n)| O(1)||
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|992. Subarrays with K Different Integers | [Go]({{< relref "/ChapterFour/0992.Subarrays-with-K-Different-Integers.md" >}})| Hard | O(n)| O(n)|❤️|
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|1004. Max Consecutive Ones III | [Go]({{< relref "/ChapterFour/1004.Max-Consecutive-Ones-III.md" >}})| Medium | O(n)| O(1) ||
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|1093. Statistics from a Large Sample | [Go]({{< relref "/ChapterFour/1093.Statistics-from-a-Large-Sample.md" >}})| Medium | O(n)| O(1) ||
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|---------------------------------------|---------------------------------|--------------------------|-----------------------|-----------|--------| |