# Solving Leetcode Interviews in Seconds with AI: Check if Array is Good


	# Introduction
	In this blog post, we will explore how to solve the LeetCode problem "2784" using AI. LeetCode is a popular platform for preparing for coding interviews, and with the help of AI tools like [Chatmagic](https://www.chatmagic.app), we can generate solutions quickly and efficiently - helping you pass the interviews and get the job offer without having to study for months.

	# Problem Statement
	> 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]. So the answer is false.  Example 2:  Input: nums = [1, 3, 3, 2] Output: true 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. It can be seen that nums is a permutation of base[3] = [1, 2, 3, 3] (by swapping the second and fourth elements in nums, we reach base[3]). Therefore, the answer is true. Example 3:  Input: nums = [1, 1] Output: true Explanation: Since the maximum element of the array is 1, the only candidate n for which this array could be a permutation of base[n], is n = 1. It can be seen that nums is a permutation of base[1] = [1, 1]. Therefore, the answer is true. Example 4:  Input: nums = [3, 4, 4, 1, 2, 1] Output: false Explanation: Since the maximum element of the array is 4, the only candidate n for which this array could be a permutation of base[n], is n = 4. However, base[4] has five elements but array nums has six. Therefore, it can not be a permutation of base[4] = [1, 2, 3, 4, 4]. So the answer is false.    Constraints:  1 <= nums.length <= 100 1 <= num[i] <= 200  

	# Explanation
	Here's the breakdown of the solution:

*   **Determine `n`:** Find the maximum element in the `nums` array. This value becomes our candidate for `n`.
*   **Length Check:** Verify if the length of `nums` is equal to `n + 1`. If not, the array cannot be a permutation of `base[n]`.
*   **Frequency Check:** Count the occurrences of each number from 1 to `n` in `nums`. Ensure that each number from 1 to `n-1` appears exactly once, and `n` appears twice.

*   **Runtime Complexity:** O(n)
*   **Storage Complexity:** O(n)

	
	# Code
	```python
	def isGood(nums):
    """
    Checks if the given array is a permutation of base[n].

    Args:
        nums (list of int): The input array.

    Returns:
        bool: True if the array is good, False otherwise.
    """

    n = max(nums)
    if len(nums) != n + 1:
        return False

    counts = {}
    for num in nums:
        counts[num] = counts.get(num, 0) + 1

    for i in range(1, n):
        if counts.get(i, 0) != 1:
            return False
    
    if counts.get(n, 0) != 2:
        return False

    return True
	```