Given an array, rotate the array to the right by k steps, where k is non-negative.
Example 1:
Input:[1,2,3,4,5,6,7]and k = 3 Output:[5,6,7,1,2,3,4]Explanation: rotate 1 steps to the right:[7,1,2,3,4,5,6]rotate 2 steps to the right:[6,7,1,2,3,4,5]rotate 3 steps to the right:[5,6,7,1,2,3,4]
Example 2:
Input: [-1,-100,3,99] and k = 2
Output: [3,99,-1,-100]
Explanation:
rotate 1 steps to the right: [99,-1,-100,3]
rotate 2 steps to the right: [3,99,-1,-100]
Note:
- Try to come up as many solutions as you can, there are at least 3 different ways to solve this problem.
- Could you do it in-place with O(1) extra space?
题目解析
思路:1 找到中心点
2.将中心点左边数据反转(不包括中心点)
3.将中心点右边数据反转(包括中心点)
4. 将反转后的数据合并
5.合并后的数据反转即可得到答案
时间复杂度为o(n) 空间复杂度为o(1)
class Solution {
public void rotate(int[] nums, int k) {
int length = nums.length;
k = k%length;
if(length==1)
return;
if(k==0)
return;
reversal(nums,0,length-k-1);
reversal(nums,length-k,length-1);
reversal(nums,0,length-1);
}
public static void reversal(int[] nums,int i,int j){
int t = 0;
while (i < j && i >= 0) {
t = nums[i];
nums[i] = nums[j];
nums[j] = t;
i++;
j--;
}
}
}