Max Consecutive Ones - Practice Coding Problems

Max Consecutive Ones - Problem

Array Easy

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

The array contains only 0s and 1s.

Input & Output

Example 1 — Basic Case

$ Input: nums = [1,1,0,1,1,1]

› Output: 3

💡 Note: The first two 1s have length 2, the last three 1s have length 3. Maximum is 3.

Example 2 — All Zeros

$ Input: nums = [0,0,0,0]

› Output: 0

💡 Note: No consecutive 1s exist, so the maximum is 0.

Example 3 — All Ones

$ Input: nums = [1,1,1,1]

› Output: 4

💡 Note: The entire array is consecutive 1s, so the maximum is 4.

Constraints

1 ≤ nums.length ≤ 10⁵
nums[i] is either 0 or 1

Visualization

Tap to expand

Understanding the Visualization

Input Array

Binary array with 0s and 1s

Find Consecutive 1s

Identify all consecutive sequences of 1s

Return Maximum

Length of longest consecutive sequence

Key Takeaway

🎯 Key Insight: Track current consecutive count and reset on zeros to find maximum streak in one pass

Asked in

G Google 15 a Amazon 12 M Microsoft 10 f Facebook 8

The key insight is to track the current consecutive count and maximum count in a single pass. The optimal approach uses O(n) time and O(1) space by resetting the current count on encountering 0 and updating the maximum whenever we see a longer streak.

Common Approaches

Approach	Time	Space	Notes
✓ Single Pass - Optimal Solution	O(n)	O(1)	Track current streak and maximum in one pass through the array
Brute Force - Check All Subarrays	O(n²)	O(1)	For each position, count consecutive 1s starting from that position

Single Pass - Optimal Solution — Algorithm Steps

Initialize current count and max count to 0
For each element, if it's 1, increment current count
If it's 0, reset current count and update max count

Visualization

Tap to expand

Step-by-Step Walkthrough

Track current streak

Count consecutive 1s, reset on 0

Update maximum

Keep track of longest streak seen

Return result

Maximum consecutive count

Code -

solution.c — C

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int solution(int* nums, int numsSize) {
    int maxCount = 0;
    int currentCount = 0;
    
    for (int i = 0; i < numsSize; i++) {
        if (nums[i] == 1) {
            currentCount++;
            if (currentCount > maxCount) {
                maxCount = currentCount;
            }
        } else {
            currentCount = 0;
        }
    }
    
    return maxCount;
}

int main() {
    char line[10000];
    fgets(line, sizeof(line), stdin);
    
    int nums[1000];
    int size = 0;
    char* token = strtok(line, "[],\n");
    while (token != NULL) {
        nums[size++] = atoi(token);
        token = strtok(NULL, "[],\n");
    }
    
    int result = solution(nums, size);
    printf("%d\n", result);
    
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(n)

Single loop iterating through array once

✓ Linear Growth

Space Complexity

O(1)

Only using constant extra variables for counting

✓ Linear Space

56.7K Views

Medium Frequency

~15 min Avg. Time

2.1K Likes

Ln 1, Col 1

Smart Actions

💡 Explanation

AI Ready

💡 Suggestion Tab to accept Esc to dismiss

// Output will appear here after running code

Code Editor Closed

Click the red button to reopen

Input & Output

Constraints

Visualization

Related Problems

Common Approaches

Single Pass - Optimal Solution — Algorithm Steps

Visualization

Code -

Time & Space Complexity

Select Compiler