Find the Longest Consecutive Run of Ones
Company: Molocoads
Role: Machine Learning Engineer
Category: Coding & Algorithms
Difficulty: medium
Interview Round: Onsite
# Find the Longest Consecutive Run of Ones
Implement `longest_ones(nums)`. Given a binary array, return the length of its longest contiguous run containing only `1` values. This prompt assumes no bit flips are allowed because the source does not specify a flip budget.
## Function Contract
`longest_ones(nums: list[int]) -> int`
## Constraints
- `0 <= len(nums) <= 1000000`
- Every element is either `0` or `1`.
- Return `0` for an empty array or an array containing no `1`.
## Examples
### Example 1
```text
Input: [1, 1, 0, 1, 1, 1]
Output: 3
```
The final three elements form the longest run.
### Example 2
```text
Input: [0, 0, 1, 1, 0, 1]
Output: 2
```
The two adjacent ones in the middle are longer than the final singleton.
Overview: Find the longest contiguous run of ones in a binary array under an explicit no-flips assumption. The prompt fixes empty-input behavior, a portable scalar return value, and two examples for later four-language console verification.
Read the full Molocoads Machine Learning Engineer interview experience this question came from
Given a binary array nums, return the length of its longest contiguous run containing only 1 values. No bit flips are allowed. Return 0 for an empty array or an array containing no 1.
Constraints
- 0 <= nums.length <= 1,000,000
- Every element is the integer 0 or 1.
- No bit flips are permitted.
- Return 0 when nums is empty or contains no 1.
Examples
Input: ([],)
Expected Output: 0
Explanation: The empty array has no run of ones.
Input: ([0],)
Expected Output: 0
Explanation: A single zero has no run of ones.
Hints
- Keep the length of the run ending at the current element.
- A zero ends the current run, while the maximum found so far remains unchanged.