LeetCode:Missing Number

Missing Number
Total Accepted: 50707 
Total Submissions: 125920 
Difficulty: Medium
Given an array containing n distinct numbers taken from  0, 1, 2, ..., n , find the one that is missing from the array.
For example, Given nums =  [0, 1, 3]  return  2 .
Note: Your algorithm should run in linear runtime complexity. Could you implement it using only constant extra space complexity?
Credits: Special thanks to @jianchao.li.fighter for adding this problem and creating all test cases.
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Array Math Bit Manipulation
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(H) First Missing Positive (M) Single Number (H) Find the Duplicate Number
c++ code:

class Solution {
public:
    int missingNumber(vector<int>& nums) {
        int ret=0;
        for(int i=0;i<nums.size();i++)
            ret ^= (i+1) ^ nums[i];
        return ret;
    }
};