按课程列出

本课属于 Coddy GDScript 学习旅程的“逻辑与流程”单元。第 47 课，共 78 课。

挑战

简单

列出选修某门课程的学生。保留你在前面步骤中写的所有内容。

1. 函数。在其他函数下面，编写 list_students_by_course(course: String) -> Array。它遍历 student_records，并按学生添加的顺序返回一个数组，其中包含选修了这门课程的学生姓名，这些学生的 "courses" 集合中包含这门课程。如果没有人选修这门课程，它会返回一个空数组。

2. 命令。在 ["show"] 上方，为 course <course> 添加一个分支，例如 course Math。它会输出 list_students_by_course() 返回的数组。对于以下命令：

add Alice 20 Math Physics
add Bob 22 Math Biology
add Diana 23 Chemistry Physics
course Math
course Physics
course Biology
course History
exit

输出为：

Student 'Alice' added successfully.
Student 'Bob' added successfully.
Student 'Diana' added successfully.
["Alice", "Bob"]
["Alice", "Diana"]
["Bob"]
[]
Goodbye!

亲手试试

extends Node

# 每个学生：姓名 -> {"age": int, "grades": Array, "courses": 课程名称的集合}
var student_records := {}

func _ready():
	while true:
		var parts := Array(OS.read_string_from_stdin().split(" ", false))
		match parts:
			["add", var student, var age, ..]:
				add_student(student, int(age), parts.slice(3))
			["grade", var student, var grade]:
				add_grade(student, int(grade))
			["enrolled", var student, var course]:
				print(is_enrolled(student, course))
			["average", var student]:
				var average := calculate_average_grade(student)
				if average >= 0:
					print("Average grade of '%s': %.2f" % [student, average])
			["show"]:
				print(student_records)
			["exit"]:
				print("Goodbye!")
				break

func add_student(student_name: String, age: int, courses: Array) -> void:
	if student_records.has(student_name):
		print("Student '%s' already exists." % student_name)
		return
	var course_set := {}
	for course in courses:
		course_set[course] = true
	student_records[student_name] = {"age": age, "grades": [], "courses": course_set}
	print("Student '%s' added successfully." % student_name)

func add_grade(student_name: String, grade: int) -> void:
	if not student_records.has(student_name):
		print("Student '%s' not found." % student_name)
		return
	student_records[student_name]["grades"].append(grade)
	print("Grade %d added for student '%s'." % [grade, student_name])

func is_enrolled(student_name: String, course: String) -> bool:
	if not student_records.has(student_name):
		print("Student '%s' not found." % student_name)
		return false
	return student_records[student_name]["courses"].has(course)

func calculate_average_grade(student_name: String) -> float:
	if not student_records.has(student_name):
		print("Student '%s' not found." % student_name)
		return -1.0
	var grades: Array = student_records[student_name]["grades"]
	if grades.is_empty():
		return 0.0
	var total := 0
	for grade in grades:
		total += grade
	return float(total) / grades.size()