Rotate Array By K

rotateByK.js

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {void} Do not return anything, modify nums in-place instead.
 */
var rotate = function(nums, k) {
    if(k > nums.length) k = k % nums.length;

    reverse(nums, 0, nums.length - 1);
    reverse(nums, 0, k - 1);
    reverse(nums, k, nums.length - 1);
};

function reverse(arr, left, right) {
    while(left < right) {
        let temp = arr[left];
        arr[left++] = arr[right];
        arr[right--] = temp;
    }
}

// Reverse the entire array first [1, 2, 3, 4, 5, 6, 7] --> [7, 6, 5, 4, 3, 2, 1]
// Reverse only the amount needed to rotate [7, 6, 5, 4, 3, 2, 1] --> [5, 6, 7, 4, 3, 2, 1]
// Reverse the rest of the array [5, 6, 7, 4, 3, 2, 1] --> [5, 6, 7, 1, 2, 3, 4]