[Swift Weekly Contest 118]LeetCode976. 三角形的最大周长 | Largest Perimeter Triangle

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. 

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:

1. 3 <= A.length <= 10000
2. 1 <= A[i] <= 10^6

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给定由一些正数（代表长度）组成的数组 A，返回由其中三个长度组成的、面积不为零的三角形的最大周长。

如果不能形成任何面积不为零的三角形，返回 0。 

示例 1：

输入：[2,1,2]
输出：5

示例 2：

输入：[1,2,1]
输出：0

示例 3：

输入：[3,2,3,4]
输出：10

示例 4：

输入：[3,6,2,3]
输出：8 

提示：

1. 3 <= A.length <= 10000
2. 1 <= A[i] <= 10^6

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324ms

 1 class Solution {
 2     func largestPerimeter(_ A: [Int]) -> Int {        
 3         var A = A.sorted(by:<)
 4         var n = A.count
 5         for i in stride(from:n-3,through:0,by:-1)
 6         {
 7             if A[i] + A[i+1] > A[i+2]
 8             {
 9                 return A[i] + A[i+1] + A[i+2]
10             }
11         }
12         return 0
13     }
14 }