LeetCode-in-Java

813. Largest Sum of Averages

Medium

You are given an integer array nums and an integer k. You can partition the array into at most k non-empty adjacent subarrays. The score of a partition is the sum of the averages of each subarray.

Note that the partition must use every integer in nums, and that the score is not necessarily an integer.

Return the maximum score you can achieve of all the possible partitions. Answers within 10-6 of the actual answer will be accepted.

Example 1:

Input: nums = [9,1,2,3,9], k = 3

Output: 20.00000

Explanation:

The best choice is to partition nums into [9], [1, 2, 3], [9]. The answer is 9 + (1 + 2 + 3) / 3 + 9 = 20.

We could have also partitioned nums into [9, 1], [2], [3, 9], for example.

That partition would lead to a score of 5 + 2 + 6 = 13, which is worse.

Example 2:

Input: nums = [1,2,3,4,5,6,7], k = 4

Output: 20.50000

Constraints:

• 1 <= nums.length <= 100
• 1 <= nums[i] <= 104
• 1 <= k <= nums.length

Solution

public class Solution {
    public double largestSumOfAverages(int[] nums, int k) {
        return helper(nums, k, 0, new Double[k + 1][nums.length]);
    }

    private double helper(int[] nums, int k, int idx, Double[][] memo) {
        if (memo[k][idx] != null) {
            return memo[k][idx];
        }
        double maxAvg = 0;
        double sum = 0;
        for (int i = idx; i <= nums.length - k; i++) {
            sum += nums[i];
            if (k - 1 > 0) {
                maxAvg = Math.max(maxAvg, (sum / (i - idx + 1)) + helper(nums, k - 1, i + 1, memo));
            } else if (i == nums.length - 1) {
                maxAvg = Math.max(maxAvg, sum / (i - idx + 1));
            }
        }
        memo[k][idx] = maxAvg;
        return maxAvg;
    }
}

This site is open source. Improve this page.