Array - 189. Rotate Array

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]

思路：

翻转数组有很多种做法，这里就只说一种 time:O(n) space:O(1),思路就是经过三次翻转数组，达到只翻转到k的目的。

代码：

java:

class Solution {
    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 void reverse(int[] nums, int start, int end) {
        int temp = 0;
        while (start < end) {
            temp = nums[start];
            nums[start] = nums[end];
            nums[end] = temp;
            start++;
            end--;
        }
    }
}

go:

func rotate(nums []int, k int)  {

    k %= len(nums)
    
    reverse(nums, 0, len(nums)-1)
    reverse(nums, 0, k-1)
    reverse(nums, k, len(nums)-1)
}

func reverse(nums []int, start, end int) {
    for ; start < end; {
        nums[start], nums[end] = nums[end], nums[start]
        start++
        end--
    }
}