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Given an array A of positive lengths, return the largest perimeter of a triangle with non-zero area, formed from 3 of these lengths.
If it is impossible to form any triangle of non-zero area, return 0.
![[leetcode] 976. Largest Perimeter Triangle](https://www.henghost.com/resour/upload/5403.png)
Example 1:
Input: [2,1,2]
Output: 5
Example 2:
Input: [1,2,1]
Output: 0
Example 3:
Input: [3,2,3,4]
Output: 10
Example 4:
Input: [3,6,2,3]
Output: 8
Note:
3 <= A.length <= 100001 <= A[i] <= 10^6分析题目的意思是：求给定数组构成的最大三角形的周长。我最开始写了三重循环暴力破解了一下，发现超时了。后面发现只需要排序然后从后往前找第一个符合三角形（两边之和大于第3边）要求的就是结果了。
代码class Solution:参考文献
def largestPerimeter(self, A: List[int]) -> int:
A.sort()
n=len(A)
for i in range(n-3,-1,-1):
if(A[i]+A[i+1]>A[i+2]):
return A[i]+A[i+1]+A[i+2]
return 0
solution
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