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.
思路: 三次反转，1：反转前部分，2：反转后部分，3：整个反转。
public class Solution {
void reverse(int[] nums, int start, int end) {
while(start < end) {
int temp = nums[start];
nums[start] = nums[end];
nums[end] = temp;
++start;
--end;
}
}
public void rotate(int[] nums, int k) {
k = k % nums.length;
reverse(nums, 0, nums.length - 1 );
reverse(nums, 0, k - 1 );
reverse(nums, k, nums.length - 1 );
}
} public class Solution {
public void rotate(int[] nums, int k) {
if(nums == null || nums.length <= 1) return;
int[] buf = new int[k];
int len = nums.length;
int shifts = k % len;
System.arraycopy(nums, len-shifts, buf, 0, shifts);
System.arraycopy(nums, 0, nums, shifts, len-shifts);
System.arraycopy(buf, 0, nums, 0, shifts);
}
} public class Solution {
public void rotate(int[] nums, int k) {
if(k==0 || nums.length==k)
return;
k = k % nums.length;
reverse(nums, 0, nums.length-k-1);
reverse(nums, nums.length-k, nums.length-1);
reverse(nums, 0, nums.length-1);
}
public void reverse(int[] nums, int left, int right){
while(left < right){
int temp = nums[left];
nums[left] = nums[right];
nums[right] = temp;
left++;
right--;
}
}
}
