Skip to main content

7. Maximum Subarray

easyAsked at Riot Games

Find the contiguous subarray with the largest sum — Riot uses Kadane to probe DP intuition before damage-window analytics questions.

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

Problem

Given an integer array, find the contiguous subarray (at least one number) which has the largest sum and return that 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. All subarrays

Try every (i,j) window and recompute the sum.

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

Tradeoff:

2. Kadane

Track the best sum ending at i; reset if it goes negative.

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:

Riot Games-specific tips

Riot reviewers like Kadane because the same running-window pattern drives damage-per-second hotspots and lag-spike windows on the server tick rate timeline.

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 Riot Games interview questions under real-loop conditions with instant feedback on your reasoning, complexity claims, and code.

Practice these live with InterviewChamp.AI →