实验6 模板类、文件I\O和异常处理

任务4

源码：

 1 #pragma once
 2 
 3 #include <iostream>
 4 #include <stdexcept>
 5 
 6 using namespace std;
 7 
 8 // 模板类声明
 9 template<typename T>
10 class Vector {
11 public:
12     Vector(int n): size{n} {
13         if(n < 0) 
14             throw length_error("Vector constructor: negtive size");
15         ptr = new T [size];
16     }
17     
18     Vector(int n, T value): size{n} {
19         if(n < 0) 
20             throw length_error("Vector constructor: negtive size");
21         ptr = new T[size];
22         for(int i = 0; i < size; i++)
23             ptr[i] = value;
24     }
25 
26     Vector(const Vector<T> &v): size{v.size}, ptr{new T[size]} {
27         for(int i = 0; i < size; i++)
28             ptr[i] = v.ptr[i];        
29     }
30     
31     ~Vector() {
32         delete [] ptr;
33     }
34 
35     int get_size() const {
36         return size;
37     }
38 
39     T& at(int index) const {
40         if(index < 0 || index >= size)
41             throw out_of_range("Vector:: at(): index out of range");
42         return ptr[index];
43     }
44 
45     T& operator[](int index) const{
46         if(index < 0 || index >= size)
47             throw out_of_range("Vector:: at(): index out of range");
48         return ptr[index];
49     }
50     
51 private:
52     int size;
53     T *ptr;
54 };
55 
56 template<typename T>
57 void output(const Vector<T> &v) {
58     for(int i = 0; i < v.get_size(); i++)
59         cout << v.at(i) << ", ";
60     cout << "\b\b \n";
61 }

 1 #include <iostream>
 2 #include "Vector.hpp"
 3 
 4 void test1() {
 5     using namespace std;
 6 
 7     int n;
 8     cout << "Enter n: ";
 9     cin >> n;
10     
11     Vector<double> x1(n);
12     for(auto i = 0; i < n; ++i)
13         x1.at(i) = i * 0.7;
14 
15     cout << "x1: "; output(x1);
16 
17     Vector<int> x2(n, 42);
18     const Vector<int> x3(x2);
19 
20     cout << "x2: "; output(x2);
21     cout << "x3: "; output(x3);
22 
23     x2.at(0) = 77;
24     x2.at(1) = 777;
25     cout << "x2: "; output(x2);
26     cout << "x3: "; output(x3);
27 }
28 
29 void test2() {
30     using namespace std;
31 
32     int n, index;
33     while(cout << "Enter n and index: ", cin >> n >> index) {
34         try {
35             Vector<int> v(n, n);
36             v.at(index) = -999;
37             cout << "v: "; output(v);
38         }
39         catch (const exception &e) {
40             cout << e.what() << endl;
41         }
42     }
43 }
44 
45 int main() {
46     cout << "测试1: 模板类接口测试\n";
47     test1();
48 
49     cout << "\n测试2: 模板类异常处理测试\n";
50     test2();
51 }

运行测试截图：

任务5

源码：

  1 #include <iostream>
  2 #include <fstream>
  3 #include <iomanip>
  4 #include <string>
  5 #include <vector>
  6 #include <algorithm>
  7 
  8 using std::string;
  9 using std::vector;
 10 using std::ostream;
 11 using std::istream;
 12 using std::cout;
 13 using std::endl;
 14 using std::setw;
 15 using std::setprecision;
 16 using std::setiosflags;
 17 using std::ios_base;
 18 
 19 
 20 class Student {
 21 public:
 22     Student() {}
 23     ~Student() {}
 24 
 25     string get_major() const { return major; }
 26     int get_score() const { return score; }
 27 
 28     friend ostream& operator<<(ostream &out, const Student &s);
 29     friend istream& operator>>(istream &in, Student &s);
 30 
 31 private:
 32     string no;          // 学号
 33     string name;        // 姓名
 34     string major;       // 专业
 35     int score;            // 分数 
 36 };
 37 
 38 // 友元函数实现
 39 // 重载流插入运算符<<
 40 ostream& operator<<(ostream &out, const Student &s) {
 41     out << setiosflags(ios_base::left);
 42     out << setw(15) << s.no
 43         << setw(15) << s.name
 44         << setw(15) << s.major
 45         << setw(5) << s.score;
 46  
 47     return out;
 48 }
 49 
 50 // 重载流提取运算符>>
 51 istream& operator>>(istream &in, Student &s) {
 52     in >> s.no >> s.name >> s.major >> s.score;
 53 
 54     return in;
 55 }
 56 
 57 
 58 // 排序函数
 59 bool compare_by_major(const Student &s1, const Student &s2) {
 60     if(s1.get_major() < s2.get_major())
 61         return true;
 62     
 63     if(s1.get_major() == s2.get_major())
 64         return s1.get_score() > s2.get_score();
 65     
 66     return false;
 67 }
 68 
 69 // 把vector<Student>对象中的元素插入到输出流out
 70 void output(ostream &out, const vector<Student> &v) {
 71     for(auto &i: v)
 72         out << i << endl;
 73 }
 74 
 75 
 76 // 把vector<Student>对象中的元素写到filename文件中
 77 void save(const string &filename, vector<Student> &v) {
 78     using std::ofstream;
 79 
 80     ofstream out(filename);
 81     if(!out.is_open()) {
 82         cout << "fail to open file to write\n";
 83         return;
 84     }
 85 
 86     output(out, v);
 87     out.close();
 88 }
 89 
 90 // 从文件filename读取学生信息到vector<Student>对象
 91 void load(const string &filename, vector<Student> &v) {
 92     using std::ifstream;
 93 
 94     ifstream in(filename);
 95     if(!in.is_open()) {
 96         cout << "fail to open file to read\n";
 97         return;
 98     }
 99 
100     string title_line;
101     getline(in, title_line);     // 跳过标题行
102 
103     Student t;
104     while(in >> t) 
105         v.push_back(t);
106 
107     in.close();
108 }
109 
110 
111 void test() {
112     using namespace std;
113 
114     vector<Student> v;
115 
116     load("data5.txt", v);   // 从文件加载选手信息到对象v
117     sort(v.begin(), v.end(), compare_by_major);  // 按解题情况排序
118     output(cout, v);    // 输出对象v中信息到屏幕
119     save("ans5.txt", v); // 把对象v中选手信息保存到文件
120 }
121 
122 int main() {
123     test();
124 }

运行测试截图：

总结：

文件读写过程中可能由于文本文档格式不同，出现乱码现象，修改格式即可