LeetCode 189. Rotate Array

Description

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].

Analysis

本题即循环右移。要记得将移位数k对n取余，即

k=kmodn

否则会多作无用功。
解法一：新建vector<int> result[n]，按右移后顺序填充数组，再赋给nums。
解法二：本地插入删除，将nums[n-k]~nums[n-1]的所有元素，插入到nums开头，然后删除最后的歌k个元素。

Code

Version 1

class Solution {public:    void rotate(vector<int>& nums, int k) {        int n = nums.size();        k %= n;        vector<int> result(n);        int i = 0;        int j = n - k;        while (j < n)            result[i++] = nums[j++];        j = 0;        while (i < n)            result[i++] = nums[j++];        nums = result;    }};

Version 2

class Solution {public:    void rotate(vector<int>& nums, int k) {        k %= nums.size();        nums.insert(nums.begin(), nums.end() - k, nums.end());        nums.erase(nums.end() - k, nums.end());    }};

Appendix

• Link: https://leetcode.com/problems/rotate-array/
• Run Time:
  
  • Version 1: 22ms
  • Version 2: 23ms
  • My first submission in Discussion…
    Link: https://discuss.leetcode.com/topic/85266/3-line-c-solution-using-insert-and-erase