268 missing number
268. Missing Number
题目: https://leetcode.com/problems/missing-number/
难度:
Medium
等差数列前n项和减去数组之和,一行瞬秒
(注意题目input从0开始取值)
class Solution(object):
def missingNumber(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
return len(nums) * (len(nums) + 1) / 2 - sum(nums)
第二种解法是位运算：位运算（异或运算）
class Solution(object):
def missingNumber(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
res = n = len(nums)
for i in range(n):
res ^= i
res ^= nums[i]
return res
