Make Array Elements Equal to Zero

You are given an integer array nums.

Start by selecting a starting position curr such that nums[curr] == 0, and choose a movement direction of either left or right.

After that, repeat the following process:

• If curr is out of the range [0, n - 1], the process ends.
• If nums[curr] == 0, move in the current direction by incrementing curr if you are moving right, or decrementing curr if you are moving left.
• Else if nums[curr] > 0:
• Decrement nums[curr] by 1.
• Reverse your movement direction: left becomes right and right becomes left.
• Take a step in your new direction.

A selection of the initial position curr and movement direction is considered valid if every element in nums becomes 0 by the end of the process.

Return the number of possible valid selections.