1695. Maximum Erasure Value

Medium

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You are given an array of positive integers nums and want to erase a subarray containing unique elements. The score you get by erasing the subarray is equal to the sum of its elements.

Return the maximum score you can get by erasing exactly one subarray.

An array b is called to be a subarray of a if it forms a contiguous subsequence of a, that is, if it is equal to a[l],a[l+1],...,a[r] for some (l,r).

Example 1:

Input: nums = [4,2,4,5,6]
Output: 17
Explanation: The optimal subarray here is [2,4,5,6].

Example 2:

Input: nums = [5,2,1,2,5,2,1,2,5]
Output: 8
Explanation: The optimal subarray here is [5,2,1] or [1,2,5].

Constraints:

• 1 <= nums.length <= 105

• 1 <= nums[i] <= 104

class Solution:
    def maximumUniqueSubarray(self, nums: List[int]) -> int:
        # Solving in same way as Longest Substring without repeating chars
        result, index = 0, 0
        d = defaultdict(lambda:-1)
        prefix_sum = self.prefix_sum(nums)
        start = 0
        while index < len(nums):
            start = max(start, d[nums[index]] +1)
            # Earlier I was using sum(nums[start : index + 1]) instaed of prefix sum
            # which was causing timeouts.
            result = max(result, (prefix_sum[index+1] - prefix_sum[start]))
            d[nums[index]] = index
            index += 1
        return result
    
    def prefix_sum(self, nums):
        result = [0]*(len(nums)+1)
        for index in range(1, len(result)):
            num = nums[index-1]
            result[index] = (num + result[index-1])
        return result