描述
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:
3 <= A.length <= 10000
1 <= A[i] <= 10^6
解析
根据题意，要找出 A 中可以形成的最大三角形长度，而且三角形的形成条件是两条边的和比第三条边大即可，所以只要将 A 降序排序，然后从头开始每三个边判断一次是否是合法三角形，如果合法则是最长的长度直接返回即可。如果不合法则继续对之后的三个边进行判断，以此类推，如果遍历完仍没有合法的最大长度，则返回 0 。
解答
class Solution(object):
def largestPerimeter(self, A):
"""
:type A: List[int]
:rtype: int
"""
A = sorted(A,reverse=True)
for i in range(2,len(A)):
if A[i-2]< A[i-1]+A[i]:
return A[i-2]+A[i-1]+A[i]
return 0
运行结果
Runtime: 144 ms, faster than 100.00% of Python online submissions for Largest Perimeter Triangle.
Memory Usage: 14.8 MB, less than 59.40% of Python online submissions for Largest Perimeter Triangle.
原题链接：leetcode.com/problems/la…
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