976. Largest Perimeter Triangle

Easy

Given an integer array nums, return the largest perimeter of a triangle with a non-zero area, formed from three of these lengths. If it is impossible to form any triangle of a non-zero area, return 0.

Example 1

Input: nums = [2,1,2]
Output: 5
Explanation: You can form a triangle with three side lengths: 1, 2, and 2.

Example 2

Input: nums = [1,2,1,10]
Output: 0
Explanation:
You cannot use the side lengths 1, 1, and 2 to form a triangle.
You cannot use the side lengths 1, 1, and 10 to form a triangle.
You cannot use the side lengths 1, 2, and 10 to form a triangle.
As we cannot use any three side lengths to form a triangle of non-zero area, we return 0.

Solution

class Solution:
    def largestPerimeter(self, nums: List[int]) -> int:
        nums.sort(reverse=True)
        for i in range(len(nums) - 2):
            a, b, c = nums[i], nums[i + 1], nums[i + 2]
            if a < b + c:
                return a + b + c
        return 0