268. Missing Number

Solution Code

C#

public class Solution {
    public int MissingNumber(int[] nums) {
        int n = nums.Length;
        int missing = n;
        
        for (int i = 0; i < n; i++)
            missing ^= i ^ nums[i];
        
        return missing;
    }
}

C++

class Solution {
public:
    int missingNumber(vector<int>& nums) {
        int n = nums.size();
        int missing = n;
        
        for (int i = 0; i < n; i++)
            missing ^= i ^ nums[i];
        
        return missing;
    }
};

Java

class Solution {
    public int missingNumber(int[] nums) {
        int n = nums.length;
        int missing = n;
        
        for (int i = 0; i < n; i++)
            missing ^= i ^ nums[i];
        
        return missing;
    }
}

Python

class Solution(object):
    def missingNumber(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        n = len(nums)
        missing = n
        
        for i in range(0, n):
            missing ^= i ^ nums[i]
        
        return missing

Ruby

# @param {Integer[]} nums
# @return {Integer}
def missing_number(nums)
    n = nums.length()
    missing = n
    n.times { |i| missing ^= i ^ nums[i] }
    missing
end

Resources

Editorial Series - LeetCode 268. Missing Number