Rotate Array 数组旋转 leetcode
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.
--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
正如note讲到， 此题有很多种解决方案。
方案一：将数组向右移动K次, 时间复杂度O(KN);
public class Solution {
public void rotate(int[] nums, int k) {
int len=nums.length;
k=k%len;
if(k==0) return ;
for(int i=0; i0; j--){
nums[j]=nums[j-1];
}
nums[0]=temp;
}
}
} 方案三： 将数组反转三次， 时间复杂度O(n), 空间复杂度O(1). 首先将数组反转, 则得到前K个元素是旋转数组的前K个元素, 只是顺序相反， 所以需要第二次反转， 后n-k 个元素也是逆序， 所以也需要反转。
例如：[1,2,3,4,5,6,7]
第一次反转[7,6,5,4,3,2,1], 第二次反转[5,6,7,4,3,2,1], 第三次反转[5, 6, 7, 1, 2, 3, 4], 即需要得到的旋转数组。
public class Solution {
public void rotate(int[] nums, int k) {
int len=nums.length;
k=k%len;
if(k==0) return ;
reverse(nums, 0, len-1);
reverse(nums, 0, k-1);
reverse(nums, k, len-1);
}
public void reverse(int[] nums, int begin, int end){
for(int i=begin, j=end; i