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Explanation: Iterator Filtering
This approach involves iterating through each record (or row) in the DataFrame and checking the 'student_id' against the specified value (101). Once a match is found, we can extract the 'name' and 'age' and return it as the result.
Time Complexity: O(n), where n is the number of students. We may have to check each student in the worst case.
Space Complexity: O(1), as no additional space beyond input storage is used.
using System.Collections.Generic;
public class Student {
public int student_id;
public string name;
public int age;
public Student(int student_id, string name, int age) {
this.student_id = student_id;
this.name = name;
this.age = age;
}
}
public class SelectData {
public static void Main() {
List<Student> students = new List<Student> {
new Student(101, "Ulysses", 13),
new Student(53, "William", 10),
new Student(128, "Henry", 6),
new Student(3, "Henry", 11)
};
foreach (var student in students) {
if (student.student_id == 101) {
Console.WriteLine("+---------+-----+");
Console.WriteLine("| {0,7} | {1,3} |", student.name, student.age);
Console.WriteLine("+---------+-----+");
break;
}
}
}
}This approach leverages a List to hold student objects in C#. Using a simple foreach loop, it searches for the student with ID 101 and prints their 'name' and 'age' using formatted strings.
Explanation: Lookup with Map/Dictionary
This approach involves using a hash table, such as a Dictionary in Python or HashMap in Java, to store each student record with their student_id as the key. This enables direct access to a record based on student_id with average O(1) complexity, extracting 'name' and 'age' immediately.
Time Complexity: O(1), as hash table operations (get) average constant time.
Space Complexity: O(n), space usage increases with input size.
1import java.util.HashMap;
2
3class Student {
4 String name;
5 int age;
6
7 Student(String name, int age) {
8 this.name = name;
9 this.age = age;
10 }
11}
12
13public class SelectData {
14 public static void main(String[] args) {
15 HashMap<Integer, Student> studentMap = new HashMap<>();
16 studentMap.put(101, new Student("Ulysses", 13));
17 studentMap.put(53, new Student("William", 10));
18 studentMap.put(128, new Student("Henry", 6));
19 studentMap.put(3, new Student("Henry", 11));
20
21 Student student = studentMap.get(101);
22 if (student != null) {
23 System.out.println("+---------+-----+");
24 System.out.println("| " + student.name + " | " + student.age + " |");
25 System.out.println("+---------+-----+");
26 }
27 }
28}Using a HashMap, students are stored with their ID as keys. By accessing studentMap.get(101), we retrieve the record instantly, allowing the program to directly print out the 'name' and 'age'.