LeetCode

3354. Make Array Elements Equal to Zero

Easy

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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, you repeat the following process:

• If curr is out of the range [0, n - 1], this 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 vice versa).
  • 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.

 

Example 1:

Input: nums = [1,0,2,0,3]

Output: 2

Explanation:

The only possible valid selections are the following:

• Choose curr = 3, and a movement direction to the left.

  <ul>
  	<li><code>[1,0,2,<strong><u>0</u></strong>,3] -&gt; [1,0,<strong><u>2</u></strong>,0,3] -&gt; [1,0,1,<strong><u>0</u></strong>,3] -&gt; [1,0,1,0,<strong><u>3</u></strong>] -&gt; [1,0,1,<strong><u>0</u></strong>,2] -&gt; [1,0,<strong><u>1</u></strong>,0,2] -&gt; [1,0,0,<strong><u>0</u></strong>,2] -&gt; [1,0,0,0,<strong><u>2</u></strong>] -&gt; [1,0,0,<strong><u>0</u></strong>,1] -&gt; [1,0,<strong><u>0</u></strong>,0,1] -&gt; [1,<strong><u>0</u></strong>,0,0,1] -&gt; [<strong><u>1</u></strong>,0,0,0,1] -&gt; [0,<strong><u>0</u></strong>,0,0,1] -&gt; [0,0,<strong><u>0</u></strong>,0,1] -&gt; [0,0,0,<strong><u>0</u></strong>,1] -&gt; [0,0,0,0,<strong><u>1</u></strong>] -&gt; [0,0,0,0,0]</code>.</li>
  </ul>
  </li>
  <li>Choose <code>curr = 3</code>, and a movement direction to the right.
  <ul>
  	<li><code>[1,0,2,<strong><u>0</u></strong>,3] -&gt; [1,0,2,0,<strong><u>3</u></strong>] -&gt; [1,0,2,<strong><u>0</u></strong>,2] -&gt; [1,0,<strong><u>2</u></strong>,0,2] -&gt; [1,0,1,<strong><u>0</u></strong>,2] -&gt; [1,0,1,0,<strong><u>2</u></strong>] -&gt; [1,0,1,<strong><u>0</u></strong>,1] -&gt; [1,0,<strong><u>1</u></strong>,0,1] -&gt; [1,0,0,<strong><u>0</u></strong>,1] -&gt; [1,0,0,0,<strong><u>1</u></strong>] -&gt; [1,0,0,<strong><u>0</u></strong>,0] -&gt; [1,0,<strong><u>0</u></strong>,0,0] -&gt; [1,<strong><u>0</u></strong>,0,0,0] -&gt; [<strong><u>1</u></strong>,0,0,0,0] -&gt; [0,0,0,0,0].</code></li>
  </ul>
  </li>
  

Example 2:

Input: nums = [2,3,4,0,4,1,0]

Output: 0

Explanation:

There are no possible valid selections.

 

Constraints:

• 1 <= nums.length <= 100
• 0 <= nums[i] <= 100
• There is at least one element i where nums[i] == 0.

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