2190\. Most Frequent Number Following Key In an Array

Easy

You are given a **0-indexed** integer array `nums`. You are also given an integer `key`, which is present in `nums`.

For every unique integer `target` in `nums`, **count** the number of times `target` immediately follows an occurrence of `key` in `nums`. In other words, count the number of indices `i` such that:

*   `0 <= i <= nums.length - 2`,
*   `nums[i] == key` and,
*   `nums[i + 1] == target`.

Return _the_ `target` _with the **maximum** count_. The test cases will be generated such that the `target` with maximum count is unique.

**Example 1:**

**Input:** nums = [1,100,200,1,100], key = 1

**Output:** 100

**Explanation:** For target = 100, there are 2 occurrences at indices 1 and 4 which follow an occurrence of key.

No other integers follow an occurrence of key, so we return 100. 

**Example 2:**

**Input:** nums = [2,2,2,2,3], key = 2

**Output:** 2

**Explanation:** For target = 2, there are 3 occurrences at indices 1, 2, and 3 which follow an occurrence of key.

For target = 3, there is only one occurrence at index 4 which follows an occurrence of key.

target = 2 has the maximum number of occurrences following an occurrence of key, so we return 2. 

**Constraints:**

*   `2 <= nums.length <= 1000`
*   `1 <= nums[i] <= 1000`
*   The test cases will be generated such that the answer is unique.