Skip to main content

26. Maximum Subarray

mediumAsked at Postman

Find the contiguous subarray with the largest sum.

By Alex Chen, Founder, InterviewChamp.AI · Last verified

Problem

Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum.

Constraints

  • 1 <= nums.length <= 10^5
  • -10^4 <= nums[i] <= 10^4

Examples

Example 1

Input
nums = [-2,1,-3,4,-1,2,1,-5,4]
Output
6

Example 2

Input
nums = [1]
Output
1

Approaches

1. Prefix sum O(n^2)

Use prefix sums; for each (i, j) compute sum[j] - sum[i-1] and track the max.

Time
O(n^2)
Space
O(n)
// build prefix; double loop over (i, j)

Tradeoff:

2. Kadane

Maintain best-ending-here = max(num, best-ending-here + num); the global best is the max over those values.

Time
O(n)
Space
O(1)
function maxSub(nums) {
  let curr = nums[0], best = nums[0];
  for (let i = 1; i < nums.length; i++) {
    curr = Math.max(nums[i], curr + nums[i]);
    best = Math.max(best, curr);
  }
  return best;
}

Tradeoff:

Postman-specific tips

Postman values Kadane verbalized as an online algorithm — request-latency rolling windows in their monitor stream use the same single-pass extend-or-restart pattern.

Solve it now

Free. No sign-up. Python and JavaScript run instantly in your browser.

Output

Press Run or Cmd+Enter to execute

Practice these live with InterviewChamp.AI

Drill Maximum Subarray and other Postman interview questions under real-loop conditions with instant feedback on your reasoning, complexity claims, and code.

Practice these live with InterviewChamp.AI →