本文正在参加「Python主题月」，详情查看 活动链接
描述
There is a function signFunc(x) that returns:
- 1 if x is positive.
- -1 if x is negative.
- 0 if x is equal to 0.
You are given an integer array nums. Let product be the product of all values in the array nums.
Return signFunc(product).
Example 1:
Input: nums = [-1,-2,-3,-4,3,2,1]
Output: 1
Explanation: The product of all values in the array is 144, and signFunc(144) = 1
Example 2:
Input: nums = [1,5,0,2,-3]
Output: 0
Explanation: The product of all values in the array is 0, and signFunc(0) = 0
Example 3:
Input: nums = [-1,1,-1,1,-1]
Output: -1
Explanation: The product of all values in the array is -1, and signFunc(-1) = -1
Note:
1 <= nums.length <= 1000
-100 <= nums[i] <= 100
解析
根据题意，就是将 nums 中的元素进行累乘之后，判断是大于 0 ，还是小于 0 ，还是等于 0 。
解答
class Solution(object):
def arraySign(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
product = reduce(lambda x,y:x*y,nums)
if product>0:
return 1
elif product<0:
return -1
return 0
运行结果
Runtime: 40 ms, faster than 91.82% of Python online submissions for Sign of the Product of an Array.
Memory Usage: 13.7 MB, less than 23.05% of Python online submissions for Sign of the Product of an Array.
解析
上面的思路按照题意来写代码，逻辑比较简单，另外我们可以换种思路，反正最后的结果就是判断乘积是不是大于 0 或者小于 0 或者等于零，按照乘法的规则，假如我们有一个任意的数字 n ，乘一个负数 -m ，结果就是 -n*m ，也就是绝对值会增加，但是会变成相反数，这样的话，只需要判断最后结果的符号即可。初始化结果 result 为 1 ，遍历 nums 中的每个元素，如果它小于零。则结果 result 变成相反 -1 ，如果元素为 0 则，直接返回 0，如果元素为正数则保持不变，遍历结束 result 即为最后的结果。
解答
class Solution(object):
def arraySign(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
result = 1
for num in nums:
if num == 0:
return 0
if num < 0:
result = -result
return result
运行结果
Runtime: 40 ms, faster than 89.67% of Python online submissions for Sign of the Product of an Array.
Memory Usage: 13.4 MB, less than 95.70% of Python online submissions for Sign of the Product of an Array.
解析
另外，我们可以用内置函数 reduce ，直接进行快速的累乘，然后判断结果的正负或者为 0 ，这种思路和第一种一样，只不过用内置函数比较方便。
解答
class Solution(object):
def arraySign(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
product = reduce(lambda x,y: x*y, nums)
return 0 if not product else 1 if product > 0 else -1
运行结果
Runtime: 48 ms, faster than 40.96% of Python online submissions for Sign of the Product of an Array.
Memory Usage: 13.6 MB, less than 48.88% of Python online submissions for Sign of the Product of an Array.
原题链接：leetcode.com/problems/si…
您的支持是我最大的动力
