Coding problem · Easy · Basics

Longest Run of Ones

Easy Algorithms & data structures

nums contains only 0s and 1s. Return the length of the longest run of consecutive 1s.

Example 1

Input: nums = [1,1,0,1,1,1]
Output: 3

Example 2

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

Hints

Hint 1

Count the current run; reset it to 0 when you see a 0.

Hint 2

Track the best run seen so far.

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Solution and explanation

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Time O(n) · Space O(1)

One pass with two counters: current grows on 1 and resets on 0, best keeps the maximum.

Reference solution

function maxConsecutiveOnes(nums) {
  let best = 0, current = 0;
  for (const n of nums) {
    current = n === 1 ? current + 1 : 0;
    best = Math.max(best, current);
  }
  return best;
}

function maxConsecutiveOnes(nums: number[]): number {
  let best = 0, current = 0;
  for (const n of nums) {
    current = n === 1 ? current + 1 : 0;
    best = Math.max(best, current);
  }
  return best;
}

def max_consecutive_ones(nums: list[int]) -> int:
    best = current = 0
    for n in nums:
        current = current + 1 if n == 1 else 0
        best = max(best, current)
    return best

<?php

function maxConsecutiveOnes(array $nums): int
{
    $best = $current = 0;
    foreach ($nums as $n) {
        $current = $n === 1 ? $current + 1 : 0;
        $best = max($best, $current);
    }
    return $best;
}

class Solution {
    public int maxConsecutiveOnes(int[] nums) {
        int best = 0, current = 0;
        for (int n : nums) {
            current = n == 1 ? current + 1 : 0;
            best = Math.max(best, current);
        }
        return best;
    }
}

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