Примерно решение:

#include <iostream>
#include <vector>
#include <map>
#include <algorithm>

int main() {
  std::map<std::string, std::vector<int>> studentsGrades{ };

  int dataLines;
  std::cin >> dataLines; // how many lines to read
  
  for (int i = 0; i < dataLines; ++i) {
    std::string studentName;
    int score;
    std::cin >> studentName >> score; // read students data
    studentsGrades[studentName].push_back(score); // add data to the map
  }

  for (auto& studentGrades : studentsGrades) {
    std::string studentName = studentGrades.first;
    std::vector<int> grades = studentGrades.second;
    
    std::sort(grades.begin(), grades.end()); // sort grades
    
    // print
    std::cout << studentName;
    for (int grade : grades) {
      std::cout << " " << grade;
    }
    std::cout << std::endl;
  }

  return 0;
}

Input:
5
Ivan 4
Maria 6
Petyr 3
Ivan 6
Maria 3


Output:
Ivan 4 6
Maria 3 6
Petyr 3