Set Mismatch

<-E 645> Set Mismatch

class Solution {
public:
    vector<int> findErrorNums(vector<int>& nums) {
        vector<int> v(nums.size() + 1), res(2);
        
        for(int i = 0; i < nums.size(); ++i)
            if(++v[nums[i]] == 2) 
                res[0] = nums[i];
        
        for(int i = 1; i < v.size(); ++i)
            if(!v[i]) { 
                res[1] = i; 
                break; 
            }
        
        return res;
    }
};