Maximum Equal Neighbor Pairs After One Value Replacement

# Maximum Equal Neighbor Pairs After One Value Replacement You are given an integer array `nums`, with positions numbered from `1` through its length. You may perform this operation at most once: choose two distinct values `x` and `y`, then replace every occurrence of `x` in the array with `y`. Return the maximum possible number of equal adjacent pairs. These are consecutive-position pairs `(1, 2)`, `(2, 3)`, and so on whose values are equal after the operation. ### Function `int maxEqualAdjacentPairs(vector<int>& nums)` ### Example 1 **Input:** `nums = [4, 4, 7, 4, 7, 9, 9]` **Output:** `5` **Explanation:** Replace every `7` with `4`, giving `[4, 4, 4, 4, 4, 9, 9]`. The first run contributes four equal adjacent pairs, and the final two `9`s contribute one, totaling `5`. ### Example 2 **Input:** `nums = [6, 6, 6, 6]` **Output:** `3` **Explanation:** Make no replacement. All three adjacent pairs are already equal. ### Constraints - `2 <= nums.length <= 100000` - `1 <= nums[i] <= 1000000000` ### Clarifications - The operation replaces all occurrences of one chosen value, not one array element. - Adjacent pairs may overlap. For example, three consecutive equal values contribute two pairs. - Only one global choice of distinct `x` and `y` is allowed, or the operation may be skipped. - Return the maximum count, not the resulting array or the chosen values. ### What a Strong Answer Covers - Accounting for a value replacement's effects across the entire array. - Counting both orientations of a neighboring value pair and preserving already-equal pairs. - Handling repeated runs and large values without inspecting every possible numeric value.