485. Max Consecutive Ones

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

Question

Given a binary array nums, return the maximum number of consecutive 1's in the array.

Example 1:

Input: nums = [1,1,0,1,1,1]
Output: 3
Explanation: The first two digits or the last three digits are consecutive 1s. The maximum number of consecutive 1s is 3.

Example 2:

Input: nums = [1,0,1,1,0,1]
Output: 2

Constraints:

• 1 <= nums.length <= 105
• nums[i] is either 0 or 1.

Approach 1: Optimal

Intuition

• Max consecutive mean track currCount & maxCount

Algorithm

1. Declare & initialize int maxCount = 0
2. Declare & initialize int currCount = 0
3. Loop through nums
   1. if (nums[i] == 0) currCount = 0
   2. else increment currCount & update maxCount
4. Return maxCount

Code

class Solution {
public:
	int findMaxConsecutiveOnes(vector<int>& nums) {
		int maxCount = 0;
		int currCount = 0;
		for (int i = 0 ; i < nums.size() ; i++) {
			if (nums[i] == 0) {
				currCount = 0;
			} else {
				currCount++;
			}
			maxCount = max(maxCount, currCount);
		}
		
		return maxCount;
	}
};

Complexity Analysis

• Time Complexity: $O(n)$ Only single pass
• Space Complexity: $O(1)$