Check if the Array Is Sorted and Rotated

LeetCode: Check if Array Is Sorted and Rotated

Problem

Given an array nums, return true if the array was originally sorted in non-decreasing order, then rotated some number of positions (including zero). Otherwise, return false.

Solution

Let's take this array for an example [3,4,5,1,2]

Observation

• Given the array was originally sorted
• So If the array has a rotation then the sort would break there let's call that a drop
• If there are multiple drops that means the array is rotated more than once and return false
• The (i+1)%lenNums wraps around so the last→first element is also checked as a drop

func check(nums []int) bool {
    lenNums := len(nums)

    drops := 0
    for i := 0; i < lenNums ; i++ {
        if nums[i] > nums[(i+1)%lenNums] {
            if (drops > 0) {
                return false
            }
            drops++
        }
    }
    return true
}