Repeat and Missing Number Array

vector<int> Solution::repeatedNumber(const vector<int> &A) {
    int n = A.size();
    vector<int> arr(n+1,0);
    vector<int> ans(2);

    for(int i=0; i<n; i++){
        if(arr[A[i]] !=0 ){
            ans[0] = A[i];
        }else{
            arr[A[i]]++;
        }
    }
    for(int i = 1; i<(n+1); i++){
        if(arr[i] == 0){
            ans[1]=i;
            break;
        }
    }
    return ans;

}