LeetCode: Check If Array Is Sorted And Rotated Solution

Approach

Count the number of increasing subarray, call this parts

• if
  parts > 1
  : totally false
• if
  parts === 0
  : totally true
• if
  parts = 1
  : check if the last elem of second part lte the first elem of first part

Implementation

1/**
2 * @param {number[]} nums
3 * @return {boolean}
4 */
5var check = function (nums) {
6  const N = nums.length
7  let parts = 0
8  for (let i = 0; i < N - 1; i++) {
9    if (nums[i] > nums[i + 1]) {
10      parts++
11    }
12  }
13  if (parts > 1) {
14    return false
15  }
16  return parts === 0 || nums[0] >= nums[N - 1]
17}