189. Rotate Array
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?
package leetcode.easy; public class RotateArray { private static void print_arr(int[] nums) { for (int num : nums) { System.out.print(num + " "); } System.out.println(); } public void rotate1(int[] nums, int k) { int temp, previous; for (int i = 0; i < k; i++) { previous = nums[nums.length - 1]; for (int j = 0; j < nums.length; j++) { temp = nums[j]; nums[j] = previous; previous = temp; } } } public void rotate2(int[] nums, int k) { int[] a = new int[nums.length]; for (int i = 0; i < nums.length; i++) { a[(i + k) % nums.length] = nums[i]; } for (int i = 0; i < nums.length; i++) { nums[i] = a[i]; } } public void rotate3(int[] nums, int k) { k = k % nums.length; int count = 0; for (int start = 0; count < nums.length; start++) { int current = start; int prev = nums[start]; do { int next = (current + k) % nums.length; int temp = nums[next]; nums[next] = prev; prev = temp; current = next; count++; } while (start != current); } } public void rotate4(int[] nums, int k) { k %= nums.length; reverse(nums, 0, nums.length - 1); reverse(nums, 0, k - 1); reverse(nums, k, nums.length - 1); } public void reverse(int[] nums, int start, int end) { while (start < end) { int temp = nums[start]; nums[start] = nums[end]; nums[end] = temp; start++; end--; } } @org.junit.Test public void test1() { int[] nums1 = { 1, 2, 3, 4, 5, 6, 7 }; int k1 = 3; int[] nums2 = { -1, -100, 3, 99 }; int k2 = 2; print_arr(nums1); rotate1(nums1, k1); print_arr(nums1); print_arr(nums2); rotate1(nums2, k2); print_arr(nums2); } @org.junit.Test public void test2() { int[] nums1 = { 1, 2, 3, 4, 5, 6, 7 }; int k1 = 3; int[] nums2 = { -1, -100, 3, 99 }; int k2 = 2; print_arr(nums1); rotate2(nums1, k1); print_arr(nums1); print_arr(nums2); rotate2(nums2, k2); print_arr(nums2); } @org.junit.Test public void test3() { int[] nums1 = { 1, 2, 3, 4, 5, 6, 7 }; int k1 = 3; int[] nums2 = { -1, -100, 3, 99 }; int k2 = 2; print_arr(nums1); rotate3(nums1, k1); print_arr(nums1); print_arr(nums2); rotate3(nums2, k2); print_arr(nums2); } @org.junit.Test public void test4() { int[] nums1 = { 1, 2, 3, 4, 5, 6, 7 }; int k1 = 3; int[] nums2 = { -1, -100, 3, 99 }; int k2 = 2; print_arr(nums1); rotate4(nums1, k1); print_arr(nums1); print_arr(nums2); rotate4(nums2, k2); print_arr(nums2); } }