Leetcode189:rotate Array

Source: Internet
Author: User

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] was rotated to [5,6,7,1,2,3,4].

Try to come up as many solutions as can, there is at least 3 different ways to solve this problem.

Rotating an array

Solution One:

Using the exchange of data, for the above n=7,k=3 situation, can be divided into three steps to complete:

    1. Exchange 1234 is 4321
    2. Exchange 567 is 765
    3. Exchange 4321765 is 5671234

Divide the operation into three steps:
Time complexity is O (N), spatial complexity is O (1)

classSolution { Public://Solution 1: Using the swap    voidRotate vector<int>& Nums,intK) {intLength=nums.size ();        K=k%length; Swapvector (Nums,0, length-k-1); Swapvector (nums,length-k,length-1); Swapvector (Nums,0, length-1); }voidSwapvector ( vector<int>&nums,intFirstintLast) { for(inti=first,j=last;i<j;i++,j--) {swap (nums[i],nums[j]); }    }};
Solution Two:

Use a new array directly to hold the data, and then copy the new array to the given array.
The time complexity is O (n), and the spatial complexity is O (n).

class Solution {public:     //直接使用一块新的内存     void rotate(vector<int>int k) {          vector<int> result;          int length=nums.size();          k%=length;          result.insert(result.end(),nums.begin()+length-k,nums.end());          result.insert(result.end(),nums.begin(),nums.begin()+length-k);          nums=result;     }};

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Leetcode189:rotate Array

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