Left Rotate array by K elements using reverse approach

#array #rotatearray #javascript #programming

Given array

const arr=[1,2,3,4,5,6]

Left Rotate array by 2 elements , Output will be ---

arr = [3,4,5,6,1,2]

This problem can be solve with reverse array approach easily

First devide the array with given K elements to rotate
In our case K is 2

Reverse the corresponding devision of elements
So after reversing the array will be

Now reverse the whole array that will give you the output
After reversing whole array the output will be

Implementation in Code level

let arr=[1,2,3,4,5,6]
let k=2

function reverseArray(arr,start,end){
    while(start<end){
        [arr[start],arr[end]]=[arr[end],arr[start]];
        start++;
        end--;
    }

    return arr;
}

//this will be the first step to reverse the first half
let reversedFirstHalf=reverseArray(arr,0,k-1)

//this will be the second step to reverse the second half
let reversedSecondHalf=reverseArray(reversedFirstHalf,k,arr.length-1)

//After reversing the whole array
let rotateArrayOutput = reverseArray(reversedSecondHalf,0,arr.length-1)