189__easy__rotate-array.js

/**
 * @param {number[]} nums
 * @param {number} k
 * @return {void} Do not return anything, modify nums in-place instead.
 */

/**
 * Using Reverse
 * O(n) time
 * O(1) space
 */
var rotate = function(nums, k) {
  k = k % nums.length;
  revs(nums, 0, nums.length - 1);
  revs(nums, 0, k - 1);
  revs(nums, k, nums.length - 1);

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

/**
 * Using Cyclic Replacements
 * O(n) time
 * O(1) space
 */
var rotate = function(nums, k) {
  let n = nums.length;
  k = k % n;
  let count = 0;
  for (let start = 0; count < nums.length; start++) {
    let currIdx = start;
    do {
      let nextIdx = (currIdx + k) % n;
      [nums[nextIdx], nums[start]] = [nums[start], nums[nextIdx]];
      currIdx = nextIdx;
      count++;
    } while (start != currIdx);
  }
};

/**
 * pop + unshift
 * O(k) time ?
 * O(n) space ?
 */
var rotate = function(nums, k) {
  k = k % nums.length;
  for (let i = 1; i <= k; i++) {
    nums.unshift(nums.pop());
  }
};

/**
 * copy array...
 *
 * O(n) time
 * O(n) space
 */
var rotate = function(nums, k) {
  k = k % nums.length;
  let n = nums.length;
  let res = new Array(n);

  for (let i = 0; i < n; i++) {
    res[i] = nums[i];
  }

  for (let i = 0; i < n; i++) {
    nums[(i + k) % n] = res[i];
  }
};