Minimum Operations to Reduce X to Zero

lcpy gen -n 1658   # by problem number
lcpy gen -s minimum_operations_to_reduce_x_to_zero   # by problem name

Input: nums = [1,1,4,2,3], x = 5
Output: 2
Explanation: The optimal solution is to remove the last two elements to reduce x to zero.

Input: nums = [5,6,7,8,9], x = 4
Output: -1

Input: nums = [3,2,20,1,1,3], x = 10
Output: 5
Explanation: The optimal solution is to remove the last three elements and the first two elements (5 operations in total) to reduce x to zero.

class Solution:
    # Time: O(n)
    # Space: O(n)
    def min_operations(self, nums: list[int], x: int) -> int:
        total = sum(nums)
        target = total - x
        n = len(nums)
        if target == 0:
            return n
        if target < 0:
            return -1
        best = -1
        first_at = {0: -1}
        prefix = 0
        for i, val in enumerate(nums):
            prefix += val
            j = first_at.get(prefix - target)
            if j is not None and i - j > best:
                best = i - j
            if prefix not in first_at:
                first_at[prefix] = i
        return n - best if best != -1 else -1