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