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

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

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

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

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

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

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

class Solution:
    def triangleNumber(self, nums: List[int]) -> int:
        if len(nums) < 3:
            return 0
        nums.sort()
    
        res = 0
        for i in range(len(nums) -1, 1, -1):
            left = 0 
            right = i - 1
            while left < right:
                if nums[i] < nums[left] + nums[right]:
                    res += right - left
                    right -= 1
                else:
                    left += 1
        return res 
            
            
16700