旋轉數組

原題

　　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.

題目大意

　　給定一個n個長度的數組，將它向右旋轉k個位置。

解題思路

　　先將k轉換成[0, n-1]內的數。再對整個數組進行翻轉，再對[0, k-1]位置的數字進行反轉，再對剩下的部分進行翻轉。

代碼實現

算法實現類

public class Solution {
    public void rotate(int[] nums, int k) {
        k = (nums.length + (k % nums.length)) % nums.length; // 保證k爲正

        int tmp;
        for (int i = 0, j = nums.length - 1; i < j; i++, j--) {
            tmp = nums[i];
            nums[i] = nums[j];
            nums[j] = tmp;
        }

        for (int i = 0, j = k - 1; i < j; i++, j--) {
            tmp = nums[i];
            nums[i] = nums[j];
            nums[j] = tmp;
        }

        for (int i = k, j = nums.length - 1; i < j; i++, j--) {
            tmp = nums[i];
            nums[i] = nums[j];
            nums[j] = tmp;
        }
    }
}