2025-08-24 12:11:09 +0000 UTC

class Solution:
    def subarraySum(self, nums: List[int]) -> int:
        sm, n = [0] * len(nums), len(nums)
        sm[0] = nums[0]
        for i in range(1, n):
            sm[i] = sm[i - 1] + nums[i]
        res = 0
        for i in range(n):
            left = max(0, i - nums[i])
            left_sum = 0
            if left > 0:
                left_sum = sm[left - 1]
            res += sm[i] - left_sum
        return res