189. Rotate Array

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#LeetCode #189 #翻转数组

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本文介绍了一种数组旋转算法，通过三次翻转实现数组元素向右旋转k步的操作。以n=7,k=3为例，详细解释了如何将数组[1,2,3,4,5,6,7]旋转为[5,6,7,1,2,3,4]的过程。

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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.

解题思路：
利用翻转的巧妙之处，
1 2 3 4 5 6 7
4 3 2 1 7 6 5
5 6 7 1 2 3 4

class Solution {
public:
    void rotate(vector<int>& nums, int k) {
        if (nums.size() < k) k = k % nums.size();

        rotate(nums, 0, nums.size() - k - 1);
        rotate(nums, nums.size() - k, nums.size() - 1);
        rotate(nums, 0, nums.size() - 1);
    }

    void rotate(vector<int>& nums, int start, int end) {
        int i = start;
        int j = end;

        while (i < j) {
            swap(nums[i++], nums[j--]);
        }
    }
};