[Leetcode 189] Rotate Array

Rotate an array of n elements to the right by K steps.

For example, with n = 7 and k = 3, the array is [1,2,3,4,5,6,7] rotated to [5,6,7,1,2,3,4] .

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

[Show hint]

Related Problem:reverse Words in a String II

[Solution]

Save A[k, n-1] to temporary space, move a[0, K-1]. O (k) Secondary storage

voidRotate (vector<int>& Nums,intk) {intn =nums.size (); if(n = =0|| K <=0)            return; K= k%N; Vector<int> buf (k,0);  for(inti =0; I < K; i++) Buf[i]= Nums[n-k +i];  for(inti = n-1; I >= K; i--) Nums[i]= Nums[i-K];  for(inti =0; I < K; i++) Nums[i]=Buf[i]; }

In situ Exchange:

The array consists of AB two parts, moving K positions to form a BA

Use R (a) to indicate the reverse order of a, then there is R (R (a)) = a

R (AB) = R (B) R (A)

Then R (B), R (A) are reversed to get BA

1 voidRotate (vector<int>& Nums,intk)2     {3         intn =nums.size ();4         if(n = =0|| K <=0)5             return;6             7K = k%N;8Reverse (Nums,0N1);9Reverse (Nums,0K1);TenReverse (nums, K, N-1); One     } A      -     voidReverse (vector<int>& Nums,intSinte) -     { the          for(inti = s, j = e; I < J; i++, j--) - swap (Nums[i], nums[j]); -}

[Leetcode 189] Rotate Array