leetcode_07_01_24.py

class Solution:
    def numberOfArithmeticSlices(self, nums: List[int]) -> int:
        n = len(nums)
        total_count = 0

        # dp[i][d] represents the number of arithmetic subsequences ending at index i with common difference d
        dp = [defaultdict(int) for _ in range(n)]

        for i in range(1, n):
            for j in range(i):
                diff = nums[i] - nums[j]

                # Check for possible integer overflow
                if diff < -2**31 or diff > 2**31 - 1:
                    continue

                count = dp[j][diff] if diff in dp[j] else 0

                # Add the count to the total and update dp[i][diff]
                total_count += count
                dp[i][diff] += count + 1

        return total_count