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g2701_2800.s2784_check_if_array_is_good.readme.md Maven / Gradle / Ivy

2784\. Check if Array is Good

Easy

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`