ArrSortRotCheck.go

/*
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.

There may be duplicates in the original array.

Note: An array A rotated by x positions results in an array B of the same length such that A[i] == B[(i+x) % A.length], where % is the modulo operation.



Example 1:

Input: nums = [3,4,5,1,2]
Output: true
Explanation: [1,2,3,4,5] is the original sorted array.
You can rotate the array by x = 3 positions to begin on the the element of value 3: [3,4,5,1,2].
Example 2:

Input: nums = [2,1,3,4]
Output: false
Explanation: There is no sorted array once rotated that can make nums.
Example 3:

Input: nums = [1,2,3]
Output: true
Explanation: [1,2,3] is the original sorted array.
You can rotate the array by x = 0 positions (i.e. no rotation) to make nums.
Example 4:

Input: nums = [1,1,1]
Output: true
Explanation: [1,1,1] is the original sorted array.
You can rotate any number of positions to make nums.
Example 5:

Input: nums = [2,1]
Output: true
Explanation: [1,2] is the original sorted array.
You can rotate the array by x = 5 positions to begin on the element of value 2: [2,1].


Constraints:

1 <= nums.length <= 100
1 <= nums[i] <= 100
*/

package main

import (
	"log"
)

func main() {
	tests := [][]int{nil, {}, {3, 4, 5, 1, 2}, {2, 1, 3, 4}, {1, 2, 3}, {1, 1, 1}, {2, 1}, {3,2,1}}

	for _, test := range tests {
		log.Printf("check(%v) = %v\n", test, check(test))
	}
}

func check(nums []int) bool {
	// make a full iteration of the array - each item should be larger than or equal to the item before*
	// * this rule may be broken once (array potentially rotated), and if so the first item should be larger than the last item

	/*
	  if len(nums) <= 0 {
	    return true // ?
	  }
	*/

	rotated := false // flag indicating the array may have been rotated by omre than zero items

	for i := 0; i < len(nums); i++ {
		if i < len(nums)-1 {
			if nums[i] > nums[i+1] {
				if !rotated {
					rotated = true
				} else {
					return false
				}
			}
		}
	}

	if rotated {
		if nums[len(nums)-1] > nums[0] {
			return false
		}
	}

	return true
}