Solve in Python:
Given an array A of positive lengths, return the largest perimeter of a triangle with non-zero area, formed from 3 of these lengths.
If it is impossible to form any triangle of non-zero area, return 0.
 



Example 1:
Input: [2,1,2]
Output: 5


Example 2:
Input: [1,2,1]
Output: 0


Example 3:
Input: [3,2,3,4]
Output: 10


Example 4:
Input: [3,6,2,3]
Output: 8

 
Note:

3 <= A.length <= 10000
1 <= A[i] <= 10^6
class Solution:
    def largestPerimeter(self, A: List[int]) -> int:
        if len(A)<3:
            return 0
        
        A.sort(reverse=True)
        
        while len(A)>2:
            max_num = A.pop(0)
            if max_num >= A[0] + A[1]:
                continue
            else:
                return max_num+A[0]+A[1]
        return 0