268. Missing Number

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268. Missing Number

Description

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:

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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:

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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:

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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 <= 10^4
  • 0 <= nums[i] <= n
  • All the numbers of nums are unique .

Follow up: Could you implement a solution using only O(1) extra space complexity and O(n) runtime complexity?

Hints/Notes

  • 2025/01/04
  • bit operation
  • No solution from 0x3F

Solution

Language: C++

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