2784. Check if Array is Good

Difficulty: Easy

Topics: Mid Level , Array , Hash Table , Sorting , Biweekly Contest 109

You are given an integer array nums . We consider an array good if it is a permutation of an array base[n] .

base[n] = [1, 2, ..., n - 1, n, n] (in other words, it is an array of length n + 1 which contains 1 to n - 1 exactly once, plus two occurrences of n ). For example, base[1] = [1, 1] and base[3] = [1, 2, 3, 3] .

Return true if the given array is good, otherwise return false .

Note: A permutation of integers represents an arrangement of these numbers.

Example 1:

Input: nums = [2, 1, 3]

Output: false

Explanation: Since the maximum element of the array is 3 , the only candidate n for which this array could be a permutation of base[n] , is n = 3 . However, base[3] has four elements but array nums has three. Therefore, it can not be a permutation of base[3] = [1, 2, 3, 3] .…