一、题目

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

二、题解

class Solution {
public:int largestPerimeter(vector<int>& nums) {int n = nums.size();sort(nums.begin(),nums.end());for(int i = n - 1;i > 1;i--){if(nums[i-2] + nums[i-1] > nums[i]){return nums[i] + nums[i-1] + nums[i-2];}}return 0;}
};