268_Missing_Number.cpp

class Solution {
public:
    int missingNumber(vector<int>& nums) {
        int n = nums.size();
   
    int expectedSum = n * (n + 1) / 2;

    int actualSum = 0;
    for (int num : nums) {
        actualSum += num;
    }

    return expectedSum - actualSum;
    }
};