[C++]Iterating Vectors with Different Size

Here are three vectors containing correct answers for each test takers, and they christmas-treed the test like below:

vector<int> solution(vector<int> answerSheet) {
    vector <int> test1 {1,2,3,4,5};
    vector <int> test2 {2, 1, 2, 3, 2, 4, 2, 5};
    vector <int> test3 {3, 3, 1, 1, 2, 2, 4, 4, 5, 5};
}

To grade the test, the correct answers are compared with answerSheet. If the size of correct answers is larger or smaller than answerSheet, it will make index error. So, we can use property of Modulus operation.

Note: The result of the modulus operation is 0 ~ N-1.

int user1=0;
int user2=0;
int user3=0;

for(int i=0; i<answerSheetheet.size(); i++){
  if(test1[i%5] == answerSheet[i]) user1++;
  if(test2[i%8] == answerSheet[i]) user2++;
  if(test3[i%10] == answerSheet[i]) user3++;
  }

Now, we can iterate three vectors at the same time and count the number of right answers for each test takers.