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The problem

A server monitor records a binary array, one entry per minute: 1 if the service was up and 0 if it was down. The reliability report needs the longest uninterrupted uptime streak, which is the longest run of consecutive 1s. It's a single pass with a running counter that resets at every 0, and it's the simplest example of the "track the current run, remember the best run" pattern that appears in many harder array problems.

Example: [1, 1, 0, 1, 1, 1] → 3.

Function signature

int findMaxConsecutiveOnes(const vector<int>& nums);  // nums contains only 0s and 1s

Test cases

Input nums	Output	Explanation
[1, 1, 0, 1, 1, 1]	3	The streak at the end
[1, 0, 1, 1, 0, 1]	2
[0, 0]	0	No 1s at all
[1]	1
[1, 1, 1, 1]	4	The whole array
[]	0

(Confirm: the array is binary; return 0 when there are no 1s.)

How interviewers phrase it

• "Find the maximum number of consecutive 1s in a binary array" (LeetCode 485).
• Harder follow-ups: "You may flip at most one 0" (LeetCode 487) or "at most k zeros" (LeetCode 1004), which need a sliding window.

Clarifying questions to ask

1. Is the array strictly binary?
2. What should be returned if there are no 1s?
3. Is flipping any zeros allowed?

Follow-ups to expect

1. "Why update the best inside the loop, not only when a 0 appears?"
2. "What if you can flip at most k zeros?"
3. "Could you do it with a streaming input?"
4. "Complexity?"

Related questions

• Reverse an array Easy
• Basic Hashing Easy
• Counting Frequencies of Array Elements Easy
• Highest Occurring Element in an Array Easy
• Largest Element Easy
• Second Largest Element Easy

All 474 dsa interview questions

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