LeetCode之Rotate Array

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.

[show hint]

Related problem: Reverse Words in a String II

Credits:
Special thanks to @Freezen for adding this problem and creating all test cases.

2、结题思路

1、先得到有效的k,

2、反转所有数组

3、反转下标从0到k的数组

4、 反转下标从k到length - 1的数组

3、代码实现

class Solution {public void rotate(int[] nums, int k) {        if (nums == null || nums.length == 0 || k <= 0)        return;        int length = nums.length;        int lastK = 0;        if (k < length)        lastK = k;        else         lastK = k % length;        if (lastK == 0)            return;        change(nums, length);        change(nums, lastK);        int i = lastK, j = length - 1;        while (i < j) {        int temp = nums[i];        nums[i] = nums[j];        nums[j] = temp;        i++;        j--;        }            }    public void change(int[] nums, int length) {    for (int i = 0; i < length / 2; ++i) {        int temp = nums[i];        nums[i] = nums[length - i - 1];        nums[length - i - 1] = temp;    }    }}