189. Rotate Array(两次反转)

 

DescriptionHintsSubmissionsDiscussSolution

 

Pick One

---

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.

[show hint]

Related problem: Reverse Words in a String II

class Solution {
    public void rotate(int[] nums, int k) {
        k%=nums.length;
        if(k==0) return;
        
    
        reverce(nums,0,nums.length-1);
        reverce(nums,0,k-1);
        reverce(nums,k,nums.length-1);
    }
    private void reverce(int[] a,int i,int j){
        for(int k = 0;k <= (j-i)/2;k++){
            swap(a,i+k,j-k);
        }
    }
    private void swap(int[] a,int i ,int j){
        int temp = a[i];
        a[i] = a[j];
        a[j] = temp;
    }
}