【LeetCode】Rotate Array
Rotate Array
Rotate an array of n elements to the right by k steps.
For example, with n = 7 and k = 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 this problem.
Credits:
Special thanks to @Freezen for adding this problem and creating all test cases.
AC代码：（Python）
1 class Solution: 2 # @param nums, a list of integer 3 # @param k, num of steps 4 # @return nothing, please modify the nums list in-place. 5 def rotate(self, nums, k): 6 n = len(nums) 7 k = k % n 8 nums[:] = 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 of old nums, but the following one just changes its reference to a new nums not the value of old nums.
因为题目要求的是：
@return nothing, please modify the nums list in-place.
类似的还有：
1 def purify(lsst): 2 lst = lsst[:] 3 for num in lsst: 4 if num % 2 == 1: 5 lst.remove(num) 6 return lst
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。