1 题目
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.
Hint:
Could you do it in-place with O(1) extra space?
Could you do it in-place with O(1) extra space?
Credits:
Special thanks to @Freezen for adding this problem and creating all test cases.
Array
2 思路
之前在《编程珠玑》里面看过,先旋转前部分,再选择后部分,最后旋转整个,可以得到结果,时间复杂度O(n),空间O(1),是一种比较好的算法。可以用于文本编辑器中行的移动。
3 代码
public void rotate(int[] nums,int k) { int len = nums.length; k %= len;//很重要防止k超过len this.partRotate(nums, 0, len - k); this.partRotate(nums, len - k, len);//至于为什么不是len - k - 1与下面的实现有关吧 this.partRotate(nums, 0, len); } public int[] partRotate(int[] nums, int head, int rear) { int temp = 0; for (int i = 0; i < (rear - head) / 2; i++) { temp = nums[head + i]; nums[head + i] = nums[rear - i - 1]; nums[rear - i - 1] = temp; } return nums; }