[Leetcode/파이썬] 918. Maximum Sum Circular Subarray

Maximum Sum Circular Subarray

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Given a circular integer array nums of length n, return the maximum possible sum of a non-empty subarray of nums.

A circular array means the end of the array connects to the beginning of the array. Formally, the next element of nums[i] is nums[(i + 1) % n] and the previous element of nums[i] is nums[(i - 1 + n) % n].

A subarray may only include each element of the fixed buffer nums at most once. Formally, for a subarray nums[i], nums[i + 1], ..., nums[j], there does not exist i <= k1, k2 <= j with k1 % n == k2 % n.

 

Example 1:

Input: nums = [1,-2,3,-2]
Output: 3
Explanation: Subarray [3] has maximum sum 3.

Example 2:

Input: nums = [5,-3,5]
Output: 10
Explanation: Subarray [5,5] has maximum sum 5 + 5 = 10.

Example 3:

Input: nums = [-3,-2,-3]
Output: -2
Explanation: Subarray [-2] has maximum sum -2.

 

Constraints:

• n == nums.length
• 1 <= n <= 3 * 104
• -3 * 104 <= nums[i] <= 3 * 104

 

class Solution:
    def maxSubarraySumCircular(self, nums: List[int]) -> int:
        curr_min_sum = curr_max_sum = max_sum = min_sum = total = nums[0]

        for num in nums[1:] :
            curr_max_sum = max(curr_max_sum + num, num)
            max_sum = max(curr_max_sum, max_sum)
            curr_min_sum = min(curr_min_sum + num, num)
            min_sum = min(curr_min_sum, min_sum)
            total += num

        circularSum = total - min_sum

        if circularSum == 0 :
            return max_sum

        return max(max_sum, circularSum)

이 문제는 패스... 이해가 잘 되지 않는다.