@@ -497,6 +497,17 @@ class Solution:
497497 from itertools import permutations
498498 return list(permutations(nums))
499499 ```
500+ ## [ 48. rotate-image 1行] ( https://leetcode.com/problems/rotate-image/ )
501+ 先转置后镜像对称
502+ ``` python
503+ class Solution :
504+ def rotate (self matrix : List[List[int ]]) -> None :
505+ """
506+ Do not return anything, modify matrix in-place instead.
507+ """
508+ matrix[:] = [i[::- 1 ] for i in zip (* matrix)]
509+ ```
510+ 加 [ :] 才会修改原列表
500511## [ 49. Group Anagrams 1行] ( https://leetcode.com/problems/group-anagrams/ )
501512``` python
502513class Solution :
@@ -989,7 +1000,7 @@ class Solution:
9891000class Solution :
9901001 def singleNumber (self nums : List[int ]) -> int :
9911002 from functools import reduce
992- return reduce (int . __xor__ , nums)
1003+ return reduce (xor , nums)
9931004```
9941005- 这里用到了异或(xor),相同的数字异或后为0,0异或任何数都等于那个数,用reduce在列表所有元素之间使用异或^,那么留下的就是那个单独的数字了
9951006## [ 138. Copy List with Random Pointer 1行] ( https://leetcode.com/problems/copy-list-with-random-pointer/ )
@@ -1379,7 +1390,7 @@ class Solution:
13791390 return int (bin (n)[2 :].zfill(32 )[::- 1 ], 2 )
13801391```
13811392- 字符串操作
1382- - [ ziff用法 ] ( https://www.runoob.com/python/att-string-zfill.html )
1393+ - [ zfill用法 ] ( https://www.runoob.com/python/att-string-zfill.html )
13831394## [ 191. Number of 1 Bits 1行] ( https://leetcode.com/problems/number-of-1-bits/ )
13841395``` python
13851396class Solution (object ):
@@ -1510,6 +1521,13 @@ class Solution:
15101521 return nums[0]
15111522 return f(r, k - len(l) - len(m))
15121523 ```
1524+ ``` python
1525+ class Solution :
1526+ def findKthLargest (self nums : List[int ], k : int ) -> int :
1527+ return nlargest(k,nums)[- 1 ]
1528+ ```
1529+ 1530+ - 用了 heapq 的 nlargest 函数,返回一个 list , 然后取最后一个
15131531## [ 217. Contains Duplicate 1行] ( https://leetcode.com/problems/contains-duplicate/ )
15141532``` python
15151533class Solution :
@@ -1765,6 +1783,19 @@ class Solution:
17651783 return False
17661784 ```
17671785 - 从矩阵右上角开始,若值比 target 大则证明这一列的值都比 target 大,继续搜索前面的列;若比 target 小说明 target 可能在后面的行中,进入下一行
1786+ ## [ 242. 有效的字母异位词 1行] ( https://leetcode.com/problems/valid-anagram/ )
1787+ ``` python
1788+ class Solution :
1789+ def isAnagram (self s : str , t : str ) -> bool :
1790+ return Counter(s) == Counter(t)
1791+ ```
1792+ - O(n) 思路等于建哈希表
1793+ ``` python
1794+ class Solution :
1795+ def isAnagram (self s : str , t : str ) -> bool :
1796+ return sorted (s) == sorted (t)
1797+ ```
1798+ - O(n log(n)) 排序后相等,原来就相等,利用 python 的 str 可以直接排序的特点
17681799## [ 258. Add Digits 1行] ( https://leetcode.com/problems/add-digits/ )
17691800``` python
17701801class Solution :
@@ -2479,6 +2510,14 @@ class Solution:
24792510 def kClosest (self points : List[List[int ]], K : int ) -> List[List[int ]]:
24802511 return sorted (points, key = lambda x : x[0 ]** 2 + x[1 ]** 2 )[:K]
24812512```
2513+ ## [ 976. 三角形的最大周长 2行] ( https://leetcode.com/problems/largest-perimeter-triangle/ )
2514+ ``` python
2515+ class Solution :
2516+ def largestPerimeter (self A : List[int ]) -> int :
2517+ A.sort(reverse = True )
2518+ return next ((i+ j+ k for i,j,k in zip (A,A[1 :],A[2 :]) if j+ k> i ),0 )
2519+ ```
2520+ - 利用 next 函数返回第一个满足条件的值,不然就返回默认值的特点
24822521## [ 1290. Convert Binary Number in a Linked List to Integer] ( https://leetcode.com/problems/convert-binary-number-in-a-linked-list-to-integer/ )
24832522``` python
24842523# Definition for singly-linked list.
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