Python O(n) time, O(1) space solutions.


  • 1
    C
    # bit manipulation
    def missingNumber1(self, nums):
        res = 0
        for i in xrange(len(nums)+1):
            res ^= i
        for num in nums:
            res ^= num
        return res
      
    # math  
    def missingNumber(self, nums):
        return len(nums)*(len(nums)+1)/2 - sum(nums)

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