LeetCode: Max Consecutive Ones

PublishedNovember 27, 2025

•1 min read

Problem:

https://leetcode.com/problems/max-consecutive-ones/description/

Code:

class Solution:
    def findMaxConsecutiveOnes(self, nums: List[int]) -> int:
        max_ones=0
        consecutive_ones=0

        for n in nums:
            if n!=0:
                consecutive_ones+=1
            else:
                max_ones=max(consecutive_ones, max_ones)
                consecutive_ones=0
        max_ones=max(consecutive_ones, max_ones)
        return max_ones

Key Points:

Goal: find the longest streak of 1s appearing back-to-back.
Keep two counters: consecutive_ones → current streak of 1s, max_ones → best (longest) streak found so far
Loop through each number:
- If the number is 1: consecutive_ones += 1
- If the number is 0: update max_ones with the current streak reset consecutive_ones to 0
After the loop:
- Check max_ones again (in case the array ends with 1s)
Final answer = max_ones
Time Complexity: O(n)
Space Complexity: O(1)

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