number-of-arithmetic-triplets

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Algorithms

You are given a 0-indexed, strictly increasing integer array <code>nums</code> and a positive integer <code>diff</code>. A triplet <code>(i, j, k)</code> is an arithmetic triplet if the following conditions are met:

<ul>
	<li><code>i &lt; j &lt; k</code>,</li>
	<li><code>nums[j] - nums[i] == diff</code>, and</li>
	<li><code>nums[k] - nums[j] == diff</code>.</li>
</ul>

Return the number of unique arithmetic triplets.

&nbsp;
Example 1:

<pre>
Input: nums = [0,1,4,6,7,10], diff = 3
Output: 2
Explanation:
(1, 2, 4) is an arithmetic triplet because both 7 - 4 == 3 and 4 - 1 == 3.
(2, 4, 5) is an arithmetic triplet because both 10 - 7 == 3 and 7 - 4 == 3. 
</pre>

Example 2:

<pre>
Input: nums = [4,5,6,7,8,9], diff = 2
Output: 2
Explanation:
(0, 2, 4) is an arithmetic triplet because both 8 - 6 == 2 and 6 - 4 == 2.
(1, 3, 5) is an arithmetic triplet because both 9 - 7 == 2 and 7 - 5 == 2.
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>3 &lt;= nums.length &lt;= 200</code></li>
	<li><code>0 &lt;= nums[i] &lt;= 200</code></li>
	<li><code>1 &lt;= diff &lt;= 50</code></li>
	<li><code>nums</code> is strictly increasing.</li>
</ul>

arithmeticTriplets

Number of Arithmetic Triplets

Two Sum

two-sum

两数之和

3Sum

3sum

三数之和

Number of Unequal Triplets in Array

number-of-unequal-triplets-in-array

数组中不等三元组的数目

Maximum Value of an Ordered Triplet I

maximum-value-of-an-ordered-triplet-i

有序三元组中的最大值 I

Minimum Sum of Mountain Triplets I

minimum-sum-of-mountain-triplets-i

元素和最小的山形三元组 I

Array

Hash Table

Two Pointers

Enumeration

给你一个下标从 0 开始、严格递增 的整数数组 <code>nums</code> 和一个正整数 <code>diff</code> 。如果满足下述全部条件，则三元组 <code>(i, j, k)</code> 就是一个 等差三元组 ：

<ul>
	<li><code>i &lt; j &lt; k</code> ，</li>
	<li><code>nums[j] - nums[i] == diff</code> 且</li>
	<li><code>nums[k] - nums[j] == diff</code></li>
</ul>

返回不同 等差三元组 的数目。

&nbsp;

示例 1：

<pre>
输入：nums = [0,1,4,6,7,10], diff = 3
输出：2
解释：
(1, 2, 4) 是等差三元组：7 - 4 == 3 且 4 - 1 == 3 。
(2, 4, 5) 是等差三元组：10 - 7 == 3 且 7 - 4 == 3 。
</pre>

示例 2：

<pre>
输入：nums = [4,5,6,7,8,9], diff = 2
输出：2
解释：
(0, 2, 4) 是等差三元组：8 - 6 == 2 且 6 - 4 == 2 。
(1, 3, 5) 是等差三元组：9 - 7 == 2 且 7 - 5 == 2 。
</pre>

&nbsp;

提示：

<ul>
	<li><code>3 &lt;= nums.length &lt;= 200</code></li>
	<li><code>0 &lt;= nums[i] &lt;= 200</code></li>
	<li><code>1 &lt;= diff &lt;= 50</code></li>
	<li><code>nums</code> 严格 递增</li>
</ul>