leetcode-problemset/leetcode-cn/problem (English)/统计数组中的美丽分割(English) [count-beautiful-splits-in-an-array].html

<p>You are given an array <code>nums</code>.</p>

<p>A split of an array <code>nums</code> is <strong>beautiful</strong> if:</p>

<ol>
	<li>The array <code>nums</code> is split into three <span data-keyword="subarray-nonempty">subarrays</span>: <code>nums1</code>, <code>nums2</code>, and <code>nums3</code>, such that <code>nums</code> can be formed by concatenating <code>nums1</code>, <code>nums2</code>, and <code>nums3</code> in that order.</li>
	<li>The subarray <code>nums1</code> is a <span data-keyword="array-prefix">prefix</span> of <code>nums2</code> <strong>OR</strong> <code>nums2</code> is a <span data-keyword="array-prefix">prefix</span> of <code>nums3</code>.</li>
</ol>

<p>Return the <strong>number of ways</strong> you can make this split.</p>

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">nums = [1,1,2,1]</span></p>

<p><strong>Output:</strong> <span class="example-io">2</span></p>

<p><strong>Explanation:</strong></p>

<p>The beautiful splits are:</p>

<ol>
	<li>A split with <code>nums1 = [1]</code>, <code>nums2 = [1,2]</code>, <code>nums3 = [1]</code>.</li>
	<li>A split with <code>nums1 = [1]</code>, <code>nums2 = [1]</code>, <code>nums3 = [2,1]</code>.</li>
</ol>
</div>

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

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">nums = [1,2,3,4]</span></p>

<p><strong>Output:</strong> <span class="example-io">0</span></p>

<p><strong>Explanation:</strong></p>

<p>There are 0 beautiful splits.</p>
</div>

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

<ul>
	<li><code>1 &lt;= nums.length &lt;= 5000</code></li>
	<li><code><font face="monospace">0 &lt;= nums[i] &lt;= 50</font></code></li>
</ul>