976. Largest Perimeter Triangle

Problem Link

Description

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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

Solution

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Python3

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