利用公式
利用(首项＋末项)*项数/2
代码
class Solution(object):
def missingNumber(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
if nums==None or len(nums)==0:
return -1
return len(nums) * (len(nums)+1) / 2 - sum(nums)
位运算
0-n异或，再对所有数字异或
代码
class Solution(object):
def missingNumber(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
res = 0
for i in range(len(nums)+1):
res ^= i
for num in nums:
res ^= num
return res
