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leetcode-problemset/leetcode-cn/problem (English)/分割数组的方案数(English) [number-of-ways-to-split-array].html
2022-05-22 11:21:15 +08:00

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<p>You are given a <strong>0-indexed</strong> integer array <code>nums</code> of length <code>n</code>.</p>
<p><code>nums</code> contains a <strong>valid split</strong> at index <code>i</code> if the following are true:</p>
<ul>
<li>The sum of the first <code>i + 1</code> elements is <strong>greater than or equal to</strong> the sum of the last <code>n - i - 1</code> elements.</li>
<li>There is <strong>at least one</strong> element to the right of <code>i</code>. That is, <code>0 &lt;= i &lt; n - 1</code>.</li>
</ul>
<p>Return <em>the number of <strong>valid splits</strong> in</em> <code>nums</code>.</p>
<p>&nbsp;</p>
<p><strong>Example 1:</strong></p>
<pre>
<strong>Input:</strong> nums = [10,4,-8,7]
<strong>Output:</strong> 2
<strong>Explanation:</strong>
There are three ways of splitting nums into two non-empty parts:
- Split nums at index 0. Then, the first part is [10], and its sum is 10. The second part is [4,-8,7], and its sum is 3. Since 10 &gt;= 3, i = 0 is a valid split.
- Split nums at index 1. Then, the first part is [10,4], and its sum is 14. The second part is [-8,7], and its sum is -1. Since 14 &gt;= -1, i = 1 is a valid split.
- Split nums at index 2. Then, the first part is [10,4,-8], and its sum is 6. The second part is [7], and its sum is 7. Since 6 &lt; 7, i = 2 is not a valid split.
Thus, the number of valid splits in nums is 2.
</pre>
<p><strong>Example 2:</strong></p>
<pre>
<strong>Input:</strong> nums = [2,3,1,0]
<strong>Output:</strong> 2
<strong>Explanation:</strong>
There are two valid splits in nums:
- Split nums at index 1. Then, the first part is [2,3], and its sum is 5. The second part is [1,0], and its sum is 1. Since 5 &gt;= 1, i = 1 is a valid split.
- Split nums at index 2. Then, the first part is [2,3,1], and its sum is 6. The second part is [0], and its sum is 0. Since 6 &gt;= 0, i = 2 is a valid split.
</pre>
<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>
<ul>
<li><code>2 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
<li><code>-10<sup>5</sup> &lt;= nums[i] &lt;= 10<sup>5</sup></code></li>
</ul>