Ways to Split Array Into Good Subarrays
<p>You are given a binary array <code>nums</code>.</p>

<p>A subarray of an array is <strong>good</strong> if it contains <strong>exactly</strong> <strong>one</strong> element with the value <code>1</code>.</p>

<p>Return <em>an integer denoting the number of ways to split the array </em><code>nums</code><em> into <strong>good</strong> subarrays</em>. As the number may be too large, return it <strong>modulo</strong> <code>10<sup>9</sup> + 7</code>.</p>

<p>A subarray is a contiguous <strong>non-empty</strong> sequence of elements within an array.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [0,1,0,0,1]
<strong>Output:</strong> 3
<strong>Explanation:</strong> There are 3 ways to split nums into good subarrays:
- [0,1] [0,0,1]
- [0,1,0] [0,1]
- [0,1,0,0] [1]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [0,1,0]
<strong>Output:</strong> 1
<strong>Explanation:</strong> There is 1 way to split nums into good subarrays:
- [0,1,0]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
	<li><code>0 &lt;= nums[i] &lt;= 1</code></li>
</ul>
Array; Math; Dynamic Programming
func numberOfGoodSubarraySplits(nums []int) int {
	const mod int = 1e9 + 7
	ans, j := 1, -1
	for i, x := range nums {
		if x == 0 {
			continue
		}
		if j > -1 {
			ans = ans * (i - j) % mod
		}
		j = i
	}
	if j == -1 {
		return 0
	}
	return ans
}