Problem URL: Largest perimeter triangle

We will sort the array in descending order and check if the sum of the first three numbers is greater than the sum of the next three numbers. If it is, we return the sum of the first three numbers. Otherwise, we return the sum of the next three numbers.

class Solution:
    def largestPerimeter(self, nums: List[int]) -> int:
        nums.sort(reverse=True)
        while len(nums)>=3 and nums[0]>=nums[1]+nums[2]:
            nums.pop(0)
        return 0 if len(nums)<3 else sum(nums[:3])

Time Complexity: O(nlogn)
Space Complexity: O(1)