Missing Number LeetCode Solution | Easy Approach

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Missing Number Given an array nums containing n distinct numbers in the range [0, n], return the only number in the range that is missing from the array.

Example 1:

Input: nums = [3,0,1]
Output: 2
Explanation: n = 3 since there are 3 numbers, so all numbers are in the range [0,3]. 2 is the missing number in the range since it does not appear in nums.

Example 2:

Input: nums = [0,1]
Output: 2
Explanation: n = 2 since there are 2 numbers, so all numbers are in the range [0,2]. 2 is the missing number in the range since it does not appear in nums.

Example 3:

Input: nums = [9,6,4,2,3,5,7,0,1]
Output: 8
Explanation: n = 9 since there are 9 numbers, so all numbers are in the range [0,9]. 8 is the missing number in the range since it does not appear in nums.

Constraints:

  • n == nums.length
  • 1 <= n <= 104
  • 0 <= nums[i] <= n
  • All the numbers of nums are unique.

Missing Number Solutions

Time: O(n)
Space: O(1)

C++

class Solution {
 public:
  int missingNumber(vector<int>& nums) {
    int ans = nums.size();

    for (int i = 0; i < nums.size(); ++i)
      ans ^= i ^ nums[i];

    return ans;
  }
};

Java

 class Solution {
  public int missingNumber(int[] nums) {
    int ans = nums.length;

    for (int i = 0; i < nums.length; ++i)
      ans ^= i ^ nums[i];

    return ans;
  }
}

Python

 class Solution:
  def missingNumber(self, nums: List[int]) -> int:
    ans = len(nums)

    for i, num in enumerate(nums):
      ans ^= i ^ num

    return ans

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