Find the First Matching Index in a Hidden Mountain Array

# Find the First Matching Index in a Hidden Mountain Array A hidden array increases strictly to one interior peak and then decreases strictly. Its length is at least three, and both sides of the peak are nonempty. Implement `Solution.findInMountainArray(target, mountainArr)`. Return the smallest index whose value equals `target`, or `-1` if the value is absent. A value may occur once on each side; in that case return the earlier index. ### Interface Access the array only through the supplied `MountainArray` object: - `get(k) -> int` returns the value at zero-based index `k`, for `0 <= k < length()`. - `length() -> int` returns the array length. You may make at most **100 calls to `get`** during one invocation. Calls to `length` do not consume that budget. Do not inspect stored values or the object's implementation. The arrays shown below are private setup data, not an extra candidate argument. ### Examples **Example 1:** The hidden array is `[2, 6, 11, 15, 11, 4]` and `target = 11`. Return `2`, even though index `4` also contains `11`. **Example 2:** The hidden array is `[1, 5, 9, 7, 3]` and `target = 6`. Return `-1`; the target lies between some stored values but is not present. ### Constraints - `3 <= mountainArr.length() <= 10_000`. - Every value and `target` is an integer in `0..1_000_000_000`. - For some `p` with `0 < p < n - 1`, values strictly increase through index `p` and strictly decrease afterward. - The hidden array stays unchanged throughout the call. - At most 100 `get` calls are permitted, including repeated reads of the same index. ### What a Strong Answer Covers - Return the earliest occurrence and distinguish absence from a valid endpoint index. - Keep all requested indices valid and justify the worst-case API-call count. - Handle the shortest array, the peak and targets appearing on only one side. ### Follow-up Questions - How should an independent test check both the result and the call limit? - Which guarantees would need reconsideration if the array allowed equal adjacent values?