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Problem

Missing Number

Easy
  • arrays
  • math

nums holds all but one of the integers from 0 to n, where n is the length of nums, and no integer appears twice. Return the integer that is not there.

Example 1
Input
nums = [4, 0, 2, 1]
Output
3
Explanation

n is 4, so the integers are 0, 1, 2, 3 and 4. Only 3 is absent from the array.

Example 2
Input
nums = [1, 2, 3]
Output
0
Explanation

n is 3, so the integers are 0, 1, 2 and 3. The array has no 0.

Example 3
Input
nums = [0, 1, 2]
Output
3
Explanation

n is 3, so the integers are 0, 1, 2 and 3. Everything below 3 is present, which makes n itself the missing one.

Constraints:

  • 1 <= nums.length <= 10^5
  • the values are distinct integers in [0, nums.length]

Follow-up: sorting the array or using a set will work. Can you do it in O(n) time with O(1) extra space?

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