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n268.py
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40 lines (36 loc) · 917 Bytes
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#!/usr/bin/python
# -*- coding: UTF-8 -*-
"""
268. Missing Number
"""
class Solution(object):
"""
位操作，骚操作，没想明白这个理论依据是什么。。
missing =4∧(0∧0)∧(1∧1)∧(2∧3)∧(3∧4)
=(4∧4)∧(0∧0)∧(1∧1)∧(3∧3)∧2
=0∧0∧0∧0∧2
=2
"""
def missingNumber_1(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
missing = len(nums)
for i in range(len(nums)):
missing ^= i ^ nums[i]
return missing
"""
用等差数列求和公式
"""
def missingNumber_2(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
length = len(nums)
expect = length * (length + 1) / 2
actual = 0
for i in range(length):
actual += nums[i]
return expect - actual