Rotate ArrayRotate an array ofnelements to the right byksteps.
For example, withn= 7 andk= 3, the array[1,2,3,4,5,6,7]is rotated to[5,6,7,1,2,3,4].
Note:
Try to come up as many solutions as you can, there are at least 3 different ways to solve thisPRoblem.
Credits:
Special thanks to@Freezenfor adding this problem and creating all test cases.
AC代码：（Python）
1classSolution:2#@param nums, a list of integer3#@param k, num of steps4#@return nothing, please modify the nums list in-place.5defrotate(self, nums, k):6n =len(nums)7k = k %n8nums[:] = nums[n-k:] + nums[:n-k]9
要注意一个问题：
A little important thing to be cautious:
nums[:] = nums[n-k:] + nums[:n-k]
can't be written as:
nums =nums[n-k:] + nums[:n-k]
on the OJ.
The previous one can truly change the value ofoldnums, but the following one just changes its reference to anewnumsnot the value ofoldnums.
因为题目要求的是：
@return nothing, please modify the nums list in-place.
类似的还有：
1defpurify(lsst):2lst =lsst[:]3fornuminlsst:4ifnum % 2 == 1:5lst.remove(num)6returnlst
这是清除 list 中的奇数，要求不要在原输入上直接修改。
注意第二行不能 写成：
lst = lsst
而应该是：
lst = lsst[:]
这样才是值相同的两个list, 否则 lst = lsst 只是一个 list 的两个引用。
值 和 引用 的问题当属 Python 里的第一大坑。