10/23 找出數組中為大的三角形周長

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.

 

Constraints:

• 3 <= nums.length <= 104
• 1 <= nums[i] <= 106

 

class Solution:

    def largestPerimeter(self, nums: List[int]) -> int:

        '兩邊和大於第3邊'

       

        nums.sort(reverse=True)

        #從最大開始找

        for i in range(len(nums)-2):

            if nums[i+2] + nums [i+1] > nums[i]:

               

                return nums[i] + nums [i+1] + nums[i+2]

        return 0