LeetCode 1793. Maximum Score of a Good Subarray

Greedy

You are given an array of integers nums (0-indexed) and an integer k.

The score of a subarray (i, j) is defined as min(nums[i], nums[i+1], ..., nums[j]) * (j - i + 1). A good subarray is a subarray where i <= k <= j.

Return the maximum possible score of a good subarray.

Example 1:

Input: nums = [1,4,3,7,4,5], k = 3
Output: 15
Explanation: The optimal subarray is (1, 5) with a score of min(4,3,7,4,5) * (5-1+1) = 3 * 5 = 15. 

Example 2:

Input: nums = [5,5,4,5,4,1,1,1], k = 0
Output: 20
Explanation: The optimal subarray is (0, 4) with a score of min(5,5,4,5,4) * (4-0+1) = 4 * 5 = 20.

Constraints:

• 1 <= nums.length <= 105

• 1 <= nums[i] <= 2 * 104

• 0 <= k < nums.length

Solution

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class Solution {
public:
    int maximumScore(vector<int>& nums, int k) {
        int mini = nums[k];
        int ans = mini;
        
        int i = k;
        int j = k;
        
        while (i > 0 || j < nums.size() - 1) {
            if (i == 0 || (j+1 < nums.size() && nums[i-1] <= nums[j+1])) {
                j++;
                mini = min(mini, nums[j]);
                ans = max(ans, mini * (j - i + 1));
            } else {
                i--;
                mini = min(mini, nums[i]);
                ans = max(ans, mini * (j - i + 1));
            }
        }
        
        return ans;
    }
};