LeetCode 189: Rotate Array

题目描述：

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.

1.整个数组rotate

2.前k个数rotate

3.后面n-k个数rotate

时间复杂度O(n)，空间复杂度O(1)

class Solution {
public:
    void rotate(int nums[], int n, int k) {
        if(nums==NULL || n<=0 || k<=0) return ;
        k = k %n;
        for(int i =0;i<n/2;i++){
            int temp = nums[i];
            nums[i] = nums[n-i-1];
            nums[n-i-1] = temp;
        }
        for(int i =0; i<k/2;i++){
            int temp = nums[i];
            nums[i] = nums[k-i-1];
            nums[k-i-1] = temp;
        }
        int start = k;
        int tail = n;
        for(int i = start; i<start+(tail-start)/2; i++){
            int temp = nums[i];
            nums[i] = nums[tail-i+start-1];
            nums[tail-i+start-1] = temp;
        }
    }
};