Rotate Array

Medium

Python

def rotate(nums,k):
    k%=len(nums)
    nums[:]=nums[-k:]+nums[:-k]

Java

public void rotate(int[] nums,int k){
    k%=nums.length;
    rev(nums,0,nums.length-1); rev(nums,0,k-1); rev(nums,k,nums.length-1);
}
void rev(int[] a,int l,int r){
    while(l<r){int t=a[l];a[l++]=a[r];a[r--]=t;}
}

Key Insight

Python slicing trivial. Java three-reverse trick.

Python → Java Differences

Python slicing one-liner
Java three-reverse algorithm
Different approaches same result

Python

def rotate(nums,k):
    k%=len(nums)
    nums[:]=nums[-k:]+nums[:-k]

Java

public void rotate(int[] nums,int k){
    k%=nums.length;
    rev(nums,0,nums.length-1); rev(nums,0,k-1); rev(nums,k,nums.length-1);
}
void rev(int[] a,int l,int r){
    while(l<r){int t=a[l];a[l++]=a[r];a[r--]=t;}
}

Algorithm Steps

1. k = k % length
2. Three reverses

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