<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 {
public:
    int triangleNumber(vector<int>& nums) {
        sort(nums.begin(),nums.end());
        int ans=0;
        for(int k=2;k<nums.size();k++)
        {
          int i=0,j=k-1;
          while(i<j)
          {
            if(nums[i]+nums[j]<=nums[k])
            {
              i++;
            }
            else if(nums[i]+nums[j]>nums[k])
            {
              ans+=j-i;
              j--;
            }
          }
        }
        return ans;
    }
};
15800