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74 lines
4.7 KiB
Markdown
74 lines
4.7 KiB
Markdown
---
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title: Bit Manipulation
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type: docs
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---
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# Bit Manipulation
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- 异或的特性。第 136 题，第 268 题，第 389 题，第 421 题，
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```go
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x ^ 0 = x
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x ^ 11111……1111 = ~x
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x ^ (~x) = 11111……1111
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x ^ x = 0
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a ^ b = c => a ^ c = b => b ^ c = a (交换律)
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a ^ b ^ c = a ^ (b ^ c) = (a ^ b）^ c (结合律)
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```
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- 构造特殊 Mask，将特殊位置放 0 或 1。
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```go
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将 x 最右边的 n 位清零， x & ( ~0 << n )
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获取 x 的第 n 位值(0 或者 1)，(x >> n) & 1
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获取 x 的第 n 位的幂值，x & (1 << (n - 1))
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仅将第 n 位置为 1，x | (1 << n)
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仅将第 n 位置为 0，x & (~(1 << n))
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将 x 最高位至第 n 位(含)清零，x & ((1 << n) - 1)
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将第 n 位至第 0 位(含)清零，x & (~((1 << (n + 1)) - 1)）
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```
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- 有特殊意义的 & 位操作运算。第 260 题，第 201 题，第 318 题，第 371 题，第 397 题，第 461 题，第 693 题，
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```go
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X & 1 == 1 判断是否是奇数(偶数)
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X & = (X - 1) 将最低位(LSB)的 1 清零
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X & -X 得到最低位(LSB)的 1
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X & ~X = 0
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```
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| Title | Solution | Difficulty | Time | Space | 收藏 |
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| ----- | :--------: | :----------: | :----: | :-----: |:-----: |
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|78. Subsets | [Go]({{< relref "/ChapterFour/0078.Subsets.md" >}})| Medium | O(n^2)| O(n)|❤️|
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|136. Single Number | [Go]({{< relref "/ChapterFour/0136.Single-Number.md" >}})| Easy | O(n)| O(1)||
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|137. Single Number II | [Go]({{< relref "/ChapterFour/0137.Single-Number-II.md" >}})| Medium | O(n)| O(1)|❤️|
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|169. Majority Element | [Go]({{< relref "/ChapterFour/0169.Majority-Element.md" >}})| Easy | O(n)| O(1)|❤️|
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|187. Repeated DNA Sequences | [Go]({{< relref "/ChapterFour/0187.Repeated-DNA-Sequences.md" >}})| Medium | O(n)| O(1)||
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|190. Reverse Bits | [Go]({{< relref "/ChapterFour/0190.Reverse-Bits.md" >}})| Easy | O(n)| O(1)|❤️|
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|191. Number of 1 Bits | [Go]({{< relref "/ChapterFour/0191.Number-of-1-Bits.md" >}})| Easy | O(n)| O(1)||
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|201. Bitwise AND of Numbers Range | [Go]({{< relref "/ChapterFour/0201.Bitwise-AND-of-Numbers-Range.md" >}})| Medium | O(n)| O(1)|❤️|
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|231. Power of Two | [Go]({{< relref "/ChapterFour/0231.Power-of-Two.md" >}})| Easy | O(1)| O(1)||
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|260. Single Number III | [Go]({{< relref "/ChapterFour/0260.Single-Number-III.md" >}})| Medium | O(n)| O(1)|❤️|
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|268. Missing Number | [Go]({{< relref "/ChapterFour/0268.Missing-Number.md" >}})| Easy | O(n)| O(1)||
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|318. Maximum Product of Word Lengths | [Go]({{< relref "/ChapterFour/0318.Maximum-Product-of-Word-Lengths.md" >}})| Medium | O(n)| O(1)||
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|338. Counting Bits | [Go]({{< relref "/ChapterFour/0338.Counting-Bits.md" >}})| Medium | O(n)| O(n)||
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|342. Power of Four | [Go]({{< relref "/ChapterFour/0342.Power-of-Four.md" >}})| Easy | O(n)| O(1)||
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|371. Sum of Two Integers | [Go]({{< relref "/ChapterFour/0371.Sum-of-Two-Integers.md" >}})| Easy | O(n)| O(1)||
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|389. Find the Difference | [Go]({{< relref "/ChapterFour/0389.Find-the-Difference.md" >}})| Easy | O(n)| O(1)||
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|393. UTF-8 Validation | [Go]({{< relref "/ChapterFour/0393.UTF-8-Validation.md" >}})| Medium | O(n)| O(1)||
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|397. Integer Replacement | [Go]({{< relref "/ChapterFour/0397.Integer-Replacement.md" >}})| Medium | O(n)| O(1)||
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|401. Binary Watch | [Go]({{< relref "/ChapterFour/0401.Binary-Watch.md" >}})| Easy | O(1)| O(1)||
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|405. Convert a Number to Hexadecimal | [Go]({{< relref "/ChapterFour/0405.Convert-a-Number-to-Hexadecimal.md" >}})| Easy | O(n)| O(1)||
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|421. Maximum XOR of Two Numbers in an Array | [Go]({{< relref "/ChapterFour/0421.Maximum-XOR-of-Two-Numbers-in-an-Array.md" >}})| Medium | O(n)| O(1)|❤️|
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|461. Hamming Distance | [Go]({{< relref "/ChapterFour/0461.Hamming-Distance.md" >}})| Easy | O(n)| O(1)||
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|476. Number Complement | [Go]({{< relref "/ChapterFour/0476.Number-Complement.md" >}})| Easy | O(n)| O(1)||
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|477. Total Hamming Distance | [Go]({{< relref "/ChapterFour/0477.Total-Hamming-Distance.md" >}})| Medium | O(n)| O(1)||
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|693. Binary Number with Alternating Bits | [Go]({{< relref "/ChapterFour/0693.Binary-Number-with-Alternating-Bits.md" >}})| Easy | O(n)| O(1)|❤️|
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|756. Pyramid Transition Matrix | [Go]({{< relref "/ChapterFour/0756.Pyramid-Transition-Matrix.md" >}})| Medium | O(n log n)| O(n)||
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|762. Prime Number of Set Bits in Binary Representation | [Go]({{< relref "/ChapterFour/0762.Prime-Number-of-Set-Bits-in-Binary-Representation.md" >}})| Easy | O(n)| O(1)||
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|784. Letter Case Permutation | [Go]({{< relref "/ChapterFour/0784.Letter-Case-Permutation.md" >}})| Easy | O(n)| O(1)||
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|898. Bitwise ORs of Subarrays | [Go]({{< relref "/ChapterFour/0898.Bitwise-ORs-of-Subarrays.md" >}})| Medium | O(n)| O(1)||
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|---------------------------------------|---------------------------------|--------------------------|-----------------------|-----------|--------| |