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;
    	}
    }
}