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`@@ -5538,6 +5538,15 @@ class Solution:`
`5538`	`5538`	`l1.next = self.mergeTwoLists(l1.next, l2)`
`5539`	`5539`	`return l1 or l2`
`5540`	`5540`	```
	`5541`	`+#### [779. 第K个语法符号](https://leetcode-cn.com/problems/k-th-symbol-in-grammar/comments/)`
	`5542`	+```python
	`5543`	`+class Solution:`
	`5544`	`+ def kthGrammar(self, N: int, K: int) -> int:`
	`5545`	`+ return 0 if N == 1 else (K + 1) % 2 ^ self.kthGrammar(N - 1, (K + 1) // 2);`
	`5546`	+```
	`5547`	+- 由于递推关系式可知第 `N` 行的第 `K` 个数计算自第 `N - 1` 行的第 `(K + 1) // 2` 个数
	`5548`	+- 我们称第 `N` 行的第 `K` 个数为C,第 `N - 1` 行的第 `(K + 1) // 2` 个数为 P
	`5549`	+- `0 → 01`,`1 → 10`,可见变换后实际上是在原来的数字后加了相对的数(这里称 0 与 1 相对),那么如果 K 为奇数则 `C = P`,否则 `C = P 的相对数`
`5541`	`5550`
`5542`	`5551`	`# 常用技巧总结`
`5543`	`5552`	`- set 中的 in 操作时间复杂度为 O(1)`

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