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补充剑指Offer58-II.左旋转字符串.md python方法

如果不让使用自带函数reversed() 可以使用该方法

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Original file line number	Diff line number	Diff line change
`@@ -136,13 +136,28 @@ class Solution:`
`136`	`136`
`137`	`137`	`# return "".join(s)`
`138`	`138`
	`139`	`+# 方法三:如果连reversed也不让使用,那么自己手写一个`
	`140`	`+class Solution:`
	`141`	`+ def reverseLeftWords(self, s: str, n: int) -> str:`
	`142`	`+ def reverse_sub(lst, left, right):`
	`143`	`+ while left < right:`
	`144`	`+ lst[left], lst[right] = lst[right], lst[left]`
	`145`	`+ left += 1`
	`146`	`+ right -= 1`
	`147`	`+`
	`148`	`+ res = list(s)`
	`149`	`+ end = len(res) - 1`
	`150`	`+ reverse_sub(res, 0, n - 1)`
	`151`	`+ reverse_sub(res, n, end)`
	`152`	`+ reverse_sub(res, 0, end)`
	`153`	`+ return ''.join(res)`
`139`	`154`
`140`	`155`	`# 时间复杂度:O(n)`
`141`	`156`	`# 空间复杂度:O(n),python的string为不可变,需要开辟同样大小的list空间来修改`
`142`	`157`	```
`143`	`158`
`144`	`159`	```python 3
`145`		`-#方法三:考虑不能用切片的情况下,利用模+下标实现`
	`160`	`+#方法四:考虑不能用切片的情况下,利用模+下标实现`
`146`	`161`	`class Solution:`
`147`	`162`	`def reverseLeftWords(self, s: str, n: int) -> str:`
`148`	`163`	`new_s = ''`

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