leetcode976之三角形最大周长

题目描述：

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。

 def largePara(A):
     A.sort(reverse=True)
     for i in range(len(A) - 2):
         if A[i] < A[i + 1] + A[i + 2]:
             return A[i] + A[i + 1] + A[i + 2]

     return 0

 print('-----------测试largepara()------------')
 A = [3, 6, 2, 3]
 l = largePara(A)
 print('l=', l)

 def largepara1(A):
     A.sort(reverse=True)
     for i in range(len(A) - 2):
         res = 0
         if A[i] < A[i + 1] + A[i + 2]:
             res = A[i] + A[i + 1] + A[i + 2]
             break

     return res

 print('===========测试largepara1()============')
 cic = largepara1(A)
 print("circu=", cic)

 def largePara2(A):
     '''
     while 循环实现，减少时空复杂度
     :param A:
     :return:
     '''
     i = 0
     A.sort(reverse=True)
     while i < len(A) - 2:
         if A[i] < A[i + 1] + A[i + 2]: return A[i] + A[i + 1] + A[i + 2]
         i = i + 1
     return 0

 print('_______-测试largePara()__________')
 circu = largePara2(A)
 print('circu=', circu)

 def largePara3(A):
     def istriangle(a, b, c):
         if a + b > c and a + c > b and b + c > a:
             return True
         else:
             return False

     A.sort(reverse=True)
     for i in range(len(A) - 2):
         if istriangle(A[i], A[i + 1], A[i + 2]):
             return A[i] + A[i + 1] + A[i + 2]

     return 0

 print("*************测试largePara3(A)***********")
 L = largePara3(A)
 print("L=", L)

输出：

-----------测试largepara()------------
l= 8
===========测试largepara1()============
circu= 8
_______-测试largePara()__________
circu= 8
*************测试largePara3(A)***********
L= 8