#include <iostream>
#include <fstream>
#include <iomanip>
#include <limits>

using namespace std;

const int MAX_STUDENTS = 100; // 最大学生数

struct StudentScore {
	string name;
	int score;
};

int main() {
	StudentScore students[MAX_STUDENTS];
	int numStudents = 0; // 实际学生数
	
	// 读取文件数据
	ifstream inFile("student_scores.txt");
	if (inFile.is_open()) {
		while (inFile >> students[numStudents].name >> students[numStudents].score) {
			numStudents++;
		}
		inFile.close();
		cout << "已从文件中读取 " << numStudents << " 个学生成绩数据." << endl;
	} else {
		cout << "无法打开文件,将从头开始." << endl;
	}
	
	while (true) {
		cout << "=== 学生成绩信息管理系统 ===" << endl;
		cout << "1. 录入学生成绩" << endl;
		cout << "2. 修改/删除学生成绩" << endl;
		cout << "3. 查看统计信息" << endl;
		cout << "4. 退出系统" << endl;
		cout << "请输入您的选择(1-4): ";
		
		int choice;
		cin >> choice;
		
		switch (choice) {
			case 1: { // 录入学生成绩
				if (numStudents == MAX_STUDENTS) {
					cout << "已达到最大学生数,无法继续录入." << endl;
					break;
				}
				cout << "请输入学生姓名: ";
				cin >> students[numStudents].name;
				cout << "请输入学生成绩(0-100): ";
				while (!(cin >> students[numStudents].score) || students[numStudents].score < 0 || students[numStudents].score > 100) {
					cout << "无效的成绩,请重新输入(0-100): ";
					cin.clear();
					cin.ignore(numeric_limits<streamsize>::max(), '\n');
				}
				numStudents++;
				cout << "学生成绩录入成功!" << endl;
				break;
			}
			case 2: { // 修改/删除学生成绩
				if (numStudents == 0) {
					cout << "当前没有任何学生成绩数据." << endl;
					break;
				}
				cout << "请输入要修改/删除的学生编号(0-" << numStudents - 1 << "): ";
				int index;
				cin >> index;
				if (index < 0 || index >= numStudents) {
					cout << "无效的编号!" << endl;
					break;
				}
				cout << "学生姓名: " << students[index].name << ", 当前成绩: " << students[index].score << endl;
				cout << "1. 修改成绩" << endl;
				cout << "2. 删除学生" << endl;
				cout << "请输入您的选择(1-2): ";
				int subChoice;
				cin >> subChoice;
				if (subChoice == 1) {
					cout << "请输入新的成绩(0-100): ";
					while (!(cin >> students[index].score) || students[index].score < 0 || students[index].score > 100) {
						cout << "无效的成绩,请重新输入(0-100): ";
						cin.clear();
						cin.ignore(numeric_limits<streamsize>::max(), '\n');
					}
					cout << "成绩修改成功!" << endl;
				} else if (subChoice == 2) {
					for (int i = index; i < numStudents - 1; i++) {
						students[i] = students[i + 1];
					}
					numStudents--;
					cout << "学生信息删除成功!" << endl;
				} else {
					cout << "无效的选择!" << endl;
				}
				break;
			}
			case 3: { // 查看统计信息
				if (numStudents == 0) {
					cout << "当前没有任何学生成绩数据." << endl;
					break;
				}
				int maxScore = 0, minScore = 100;
				int totalScore = 0;
				for (int i = 0; i < numStudents; i++) {
					if (students[i].score > maxScore) {
						maxScore = students[i].score;
					}
					if (students[i].score < minScore) {
						minScore = students[i].score;
					}
					totalScore += students[i].score;
				}
				double avgScore = static_cast<double>(totalScore) / numStudents;
				cout << "学生成绩统计信息:" << endl;
				cout << "最高分: " << maxScore << endl;
				cout << "最低分: " << minScore << endl;
				cout << "平均分: " << fixed << setprecision(2) << avgScore << endl;
				break;
			}
			case 4: { // 退出系统
				// 保存数据到文件
				ofstream outFile("student_scores.txt");
				if (outFile.is_open()) {
					for (int i = 0; i < numStudents; i++) {
						outFile << students[i].name << " " << students[i].score << endl;
					}
					outFile.close();
					cout << "学生成绩数据已保存到文件." << endl;
				} else {
					cout << "无法打开文件,学生成绩数据未保存." << endl;
				}
				cout << "程序已退出." << endl;
				return 0;
			}
		default:
			cout << "无效的选择,请重试." << endl;
			break;
		}
	}
	
	return 0;
}