【C++ Primer Plus】编程练习答案——第17章

 1 // chapter17.h
 2 
 3 #ifndef LEARN_CPP_CHAPTER17_H
 4 #define LEARN_CPP_CHAPTER17_H
 5 
 6 #include <iostream>
 7 #include <fstream>
 8 #include <vector>
 9 #include <algorithm>
10 #include <cstring>
11 
12 void ch17_1();
13 void ch17_2(const std::string filename);
14 void ch17_3(const std::string infilename, const std::string outfilename);
15 void ch17_4(const std::string infilename1, const std::string infilename2, const std::string outfilename);
16 void ch17_5(const std::string matfile, const std::string patfile, const std::string matnpatfile);
17 void ch17_6();
18 void ShowStr(const std::string & str);
19 void GetStrs(std::ifstream & fin, std::vector<std::string> & vistr);
20 void ch17_7();
21 
22 class Store {
23 private:
24     char * str;
25     std::ofstream * outf;
26 public:
27     Store(std::ofstream & fout) : outf(&fout) {
28         str = new char[1024];
29     }
30     Store(const Store & s) {
31         if (this == &s)
32             delete [] str;
33         str = new char[1024];
34         strcpy(str, s.str);
35         outf = s.outf;
36     }
37     bool operator()(const std::string & s) {
38         int len = s.size();
39         if (outf->is_open()) {
40             outf -> write((char *)&len, sizeof(int));
41             outf -> write(s.data(), len);
42             return true;
43         }
44         else {
45             exit(EXIT_FAILURE);
46             return false;
47         }
48     }
49 };
50 
51 
52 #endif //LEARN_CPP_CHAPTER17_H

  1 // chapter17.cpp
  2 
  3 #include "chapter17.h"
  4 
  5 void ch17_1() {
  6     using namespace std;
  7     int count = 0;
  8     char ch;
  9     cout << "input some sentences: " << endl;
 10     while (cin.get(ch)) {
 11         if (ch == '$')
 12             break;
 13         ++ count;
 14     }
 15     cout << count << " chars before '$'" << endl;
 16 }
 17 
 18 void ch17_2(const std::string filename) {
 19     using namespace std;
 20     ofstream outFile(filename, ios_base::out | ios_base::trunc);
 21     if (!outFile.is_open())
 22         cerr << "file not opened" << endl;
 23     char ch;
 24     while ((ch = cin.get()) != EOF) {
 25         outFile << ch;
 26     }
 27     outFile.close();
 28 }
 29 
 30 void ch17_3(const std::string infilename, const std::string outfilename) {
 31     using namespace std;
 32     ifstream inFile;
 33     ofstream outFile;
 34     //inFile.open(infilename, ios_base::in);
 35     //outFile.open(outfilename, ios_base::out | ios_base::trunc);
 36     inFile.open(infilename, ios_base::binary | ios_base::in);
 37     outFile.open(outfilename, ios_base::binary | ios_base::out | ios_base::trunc);
 38     if (!inFile.is_open() || !outFile.is_open()) {
 39         cerr << "file not opened" << endl;
 40         exit(1);
 41     }
 42     char ch;
 43 //    while (inFile.get(ch)) {
 44 //        outFile << ch;
 45 //        cout << ch;
 46 //    }
 47     while (!inFile.eof()) {
 48         inFile.read(&ch, sizeof(char));
 49         if (inFile.eof()) break; // 去掉多余的一行
 50         outFile.write(&ch, sizeof(char));
 51     }
 52     inFile.close();
 53     outFile.close();
 54     cout << "done" << endl;
 55 }
 56 
 57 void ch17_4(const std::string infilename1, const std::string infilename2, const std::string outfilename) {
 58     using namespace std;
 59     ifstream inFile1, inFile2;
 60     ofstream outFile;
 61     inFile1.open(infilename1, ios_base::in);
 62     inFile2.open(infilename2, ios_base::in);
 63     outFile.open(outfilename, ios_base::out | ios_base::trunc);
 64     if (!inFile1.is_open() || !inFile2.is_open() || !outFile.is_open()) {
 65         cerr << "file not opened" << endl;
 66         exit(1);
 67     }
 68     while (!inFile1.eof() && !inFile2.eof()) {
 69         char temp1[1024], temp2[1024];
 70         inFile1.getline(temp1, 1024);
 71         inFile2.getline(temp2, 1024);
 72         outFile << temp1 << ' ' << temp2 << endl;
 73     }
 74     char temp[1024];
 75     while (inFile1.getline(temp, 1024))
 76         outFile << temp;
 77     while (inFile2.getline(temp, 1024))
 78         outFile << temp;
 79     inFile1.close();
 80     inFile2.close();
 81     outFile.close();
 82     cout << "done" << endl;
 83 
 84 }
 85 
 86 void ch17_5(const std::string matfile, const std::string patfile, const std::string matnpatfile) {
 87     using namespace std;
 88     ifstream inMat, inPat;
 89     ofstream outMnP;
 90     inMat.open(matfile, ios_base::in);
 91     inPat.open(patfile, ios_base::in);
 92     outMnP.open(matnpatfile, ios_base::out | ios_base::trunc);
 93     if (!inMat.is_open() || !inPat.is_open() || !outMnP.is_open()) {
 94         cerr << "file not opened" << endl;
 95         exit(1);
 96     }
 97     vector<string> mat, pat;
 98     char temp[1024];
 99     while (inMat.getline(temp, 1024))
100         mat.push_back(temp);
101     while (inPat.getline(temp, 1024))
102         pat.push_back(temp);
103     sort(mat.begin(), mat.end());
104     sort(pat.begin(), pat.end());
105     vector<string> mer(mat.size() + pat.size());
106     merge(mat.begin(), mat.end(), pat.begin(), pat.end(), mer.begin());
107     for (auto i = mer.begin(); i < mer.end(); ++ i) {
108         if (i < mer.end() && *i == *(i + 1))
109             continue;
110         outMnP << *i << endl;
111     }
112     inMat.close();
113     inPat.close();
114     outMnP.close();
115     cout << "done" << endl;
116 }
117 
118 void ch17_6() {
119     using namespace std;
120 　　// 瑞了，不想写了
121 }
122 
123 void ShowStr(const std::string & str) {
124     using namespace std;
125     cout << str << endl;
126 }
127 
128 void GetStrs(std::ifstream & fin, std::vector<std::string> & vistr) {
129     int len;
130     while (fin.read((char *)&len, sizeof(int))) {
131         char * temp = new char[len];
132         fin.read(temp, len);
133         vistr.push_back(temp);
134         delete [] temp;
135     }
136 }
137 
138 void ch17_7() {
139     using namespace std;
140     vector<string> vostr;
141     string temp;
142     // acquire strings
143     cout << "Enter strings (empty line to quit) :" << endl;
144     while (getline(cin, temp) && temp[0] != '')
145         vostr.push_back(temp);
146     cout << "Here is your input." << endl;
147     for_each(vostr.begin(), vostr.end(), ShowStr);
148     // store in a file
149     ofstream fout("./C++PrimerPlus/testfiles/strings.dat", ios_base::out | ios_base::binary);
150     for_each(vostr.begin(), vostr.end(), Store(fout));
151     fout.close();
152     // recover file contents
153     vector<string> vistr;
154     ifstream fin("./C++PrimerPlus/testfiles/strings.dat", ios_base::in | ios_base::binary);
155     if (!fin.is_open()) {
156         cerr << "Could not open file for input." << endl;
157         exit(EXIT_FAILURE);
158     }
159     GetStrs(fin, vistr);
160     cout << endl << "Here are the strings read from the file:" << endl;
161     for_each(vistr.begin(), vistr.end(), ShowStr);
162 }