valid-triangle-number

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python

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Algorithms

Given an integer array <code>nums</code>, return the number of triplets chosen from the array that can make triangles if we take them as side lengths of a triangle.

&nbsp;
Example 1:

<pre>
Input: nums = [2,2,3,4]
Output: 3
Explanation: Valid combinations are: 
2,3,4 (using the first 2)
2,3,4 (using the second 2)
2,2,3
</pre>

Example 2:

<pre>
Input: nums = [4,2,3,4]
Output: 4
</pre>

&nbsp;
Constraints:

<ul>
	<li><code>1 &lt;= nums.length &lt;= 1000</code></li>
	<li><code>0 &lt;= nums[i] &lt;= 1000</code></li>
</ul>

triangleNumber

Valid Triangle Number

3Sum Smaller

3sum-smaller

较小的三数之和

Find Polygon With the Largest Perimeter

find-polygon-with-the-largest-perimeter

找到最大周长的多边形

Greedy

Array

Two Pointers

Binary Search

Sorting

给定一个包含非负整数的数组&nbsp;<code>nums</code> ，返回其中可以组成三角形三条边的三元组个数。

&nbsp;

示例 1:

<pre>
输入: nums = [2,2,3,4]
输出: 3
解释:有效的组合是: 
2,3,4 (使用第一个 2)
2,3,4 (使用第二个 2)
2,2,3
</pre>

示例 2:

<pre>
输入: nums = [4,2,3,4]
输出: 4</pre>

&nbsp;

提示:

<ul>
	<li><code>1 &lt;= nums.length &lt;= 1000</code></li>
	<li><code>0 &lt;= nums[i] &lt;= 1000</code></li>
</ul>