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7. Maximum Subarray

easyAsked at Gojek

Find the contiguous subarray with the largest sum and return that 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. Brute force

Enumerate every subarray and track the max sum.

Time
O(n^2)
Space
O(1)
let best = -Infinity;
for (let i = 0; i < n; i++) {
  let s = 0;
  for (let j = i; j < n; j++) {
    s += nums[j];
    best = Math.max(best, s);
  }
}

Tradeoff:

2. Kadane's algorithm

At each index keep the better of (extend prior subarray) or (start fresh). One linear sweep gives the global max.

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

Tradeoff:

Gojek-specific tips

Gojek runs as a SEA super-app where streaming-aggregation patterns like Kadane show up in surge-pricing and driver-supply telemetry; show that you can fold a problem into one pass.

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Output

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