Rotate Array

[kokocan12]

Problem

When an array is given, rotate the array by k steps.

example
Input: nums = [1,2,3,4,5,6,7], k = 3
Output: [5,6,7,1,2,3,4]

Approach

First, flip the elements in array right and left.
If nums = [1,2,3,4,5,6], the fliped nums is [6,5,4,3,2,1].
Then divide left, right portion by k, [6,5] [4,3,2,1] (k is 2 in this case).
Swap each portion. [5,6] [1,2,3,4].

The code is below

const rotate = function(nums, k) {
    k = k % nums.length;
    
    // Swap all elements.
    let left = 0;
    let right = nums.length - 1;
    
    while(left < right) {
        swap(nums, left, right);
        left += 1;
        right -= 1;
    }
    
    // Swap left portion elements.
    left = 0;
    right = k-1;
    while(left < right) {
        swap(nums, left, right);
        left += 1;
        right -= 1;
    }
    
    // Swap right portion elements.
    left = k;
    right = nums.length - 1;
    while(left < right) {
        swap(nums, left, right);
        left += 1;
        right -= 1;
    }
    
};

function swap(nums, i, j) {
    const temp = nums[i];
    nums[i] = nums[j];
    nums[j] = temp;
}