Lesson N.9 of July 24, 2014

C and C++ string

File example14.cc

:open:
 1/*
 2
 3  Inheritance and usage of it
 4
 5*/
 6
 7#include <iostream>
 8#include <iomanip>
 9#include <vector>
10#include <cmath>
11
12#include <string.h> // for strlen
13#include <string> // C++ string
14
15using namespace std ;
16
17/*
18
19 print character inserted by number
20
21*/
22
23int
24main() {
25  cout << "Digit 0\n" ;
26  cout << "Digit \x30\n" ;
27
28  cout << "Letter ~\n" ;
29  cout << "Letter \x7E\n" ;
30  
31  char const * a_C_string = "I am a string" ; // pointer to a constant piece of memory
32  for ( int i = 0 ; i <= strlen(a_C_string) ; ++i )
33    cout << i << "-th character is: "
34         << a_C_string[i]
35         << " hex: " << hex << int(a_C_string[i]) << dec // reset to decimal
36         << '\n' ; 
37  
38  string a_Cpp_string = "I am a string" ; 
39  
40  cout << "C++ string: " << a_Cpp_string << '\n' ;
41  cout << "length: " << a_Cpp_string.length() << '\n' ;
42  sort( a_Cpp_string.begin(), a_Cpp_string.end()) ;
43  cout << "Sorted: " << a_Cpp_string << '\n' ;
44  reverse( a_Cpp_string.begin(), a_Cpp_string.end()) ;
45  cout << "Reversed: " << a_Cpp_string << '\n' ;
46  
47  string str1 = "I am string1" ; 
48  string str2 = "I am string2" ; 
49  string str = str1 + str2 ;
50  
51  cout << "Concatenated: " << str << '\n' ;
52  cout << "str[1] " << str[1] << '\n' ;
53  cout << "str[5] " << str[5] << '\n' ;
54  cout << "str[3] " << str[3] << '\n' ;
55  
56  return 0 ;
57}

Divisors of a number

File example15.cc

:open:
  1/*
  2
  3  Build a tree with the divisors of a number
  4
  5*/
  6
  7#include <iostream>
  8#include <iomanip>
  9#include <vector>
 10#include <cmath>
 11
 12#include <string> // C++ string
 13
 14using namespace std ;
 15
 16class Node {
 17  int           number ;
 18  vector<Node*> childs ;
 19  
 20  void free() ;
 21
 22public:
 23
 24  Node() : number(1) {    
 25    cout << "Enter to the contructor of Node\n" ;
 26  }
 27
 28  Node( int n ) : number(1) {    
 29    cout << "Enter to the contructor of Node(" << n << ")\n" ;
 30    build( n ) ;
 31  }
 32
 33  ~Node() ;
 34
 35  void build( int n ) ;
 36  void print( ostream &, int level = 0 ) ;
 37  void to_dag( ostream &, int level = 0 ) ;
 38  void to_tree( ostream &, int level = 0 ) ;
 39
 40} ;
 41
 42void
 43Node::free() {
 44  cout << "Enter to the destructor of Node (" << number << ")\n" ;
 45  for ( vector<Node*>::iterator it = childs.begin() ; it != childs.end() ; ++it )
 46    delete *it ; // *it is a pointer to the corresponding child Node
 47                 // call the destroyer for the Node *it
 48  childs.clear() ;
 49}
 50
 51Node::~Node() {
 52  free() ;
 53}
 54
 55void
 56Node::build( int n ) {
 57  //cout << "Enter build for number " << n << "\n" ;
 58  if ( number != 1 ) free() ;
 59  number = n ;
 60  // search for the divisors
 61  for ( int i = 2 ; i < n ; ++i ) {
 62    if ( (n % i) == 0 ) { // found a divisor
 63      //cout << "found divisor: " << i << " for number " << number << '\n' ;
 64      Node * pChild = new Node(i) ; // allocate the new divisor `i`
 65      //pChild->build(i) ; // compute the divisor of i
 66      childs.push_back(pChild) ; // add to the list of child od `number`
 67    }
 68  }
 69  //cout << "Exit build for number " << n << "\n" ;
 70}
 71
 72void
 73Node::print( ostream & stream, int level ) {
 74  stream << std::string(level*4, ' ') ;
 75  stream << number << '\n' ;
 76  for ( int i = 0 ; i < childs.size() ; ++i )
 77    childs[i]->print( stream, level + 1 ) ;
 78}
 79
 80void
 81Node::to_dag( ostream & stream, int level ) {
 82  if ( level == 0 ) stream << "digraph divisor_of_" << number << " {\n" ;
 83  for ( int i = 0 ; i < childs.size() ; ++i ) {
 84    stream << "  " << number << " -> " << childs[i]->number << ";\n" ;
 85    childs[i]->to_dag( stream, level + 1 ) ;
 86  }
 87  if ( level == 0 ) stream << "}\n" ;
 88}
 89
 90
 91int
 92main() {
 93  Node n(12) ;
 94  n.to_dag(cout) ;
 95
 96  //n.build(234) ;
 97  //n.to_dag(cout) ;
 98
 99  return 0 ;
100}

Convert integer to letters

File num_to_string.hh

:open:
 1#ifndef NUM_TO_STRING_HH
 2#define NUM_TO_STRING_HH
 3
 4#include <string> // C++ string
 5#include <vector> // C++ string
 6
 7class NumToString {
 8  std::vector<std::string> first20 ;
 9  std::vector<std::string> tens ;
10
11  std::string to_string_less_than_1000( int ) const ;  
12
13public:
14  NumToString() ;
15  ~NumToString() ;
16  std::string to_string( int ) const ;  
17} ;
18
19#endif

File num_to_string.cc

:open:
 1#include "num_to_string.hh"
 2
 3using namespace std ;
 4
 5NumToString::NumToString() {
 6  first20.clear() ;
 7  first20.reserve(20) ;
 8  first20.push_back("") ;
 9  first20.push_back("one") ;
10  first20.push_back("two") ;
11  first20.push_back("three") ;
12  first20.push_back("four") ;
13  first20.push_back("five") ;
14  first20.push_back("six") ;
15  first20.push_back("seven") ;
16  first20.push_back("eight") ;
17  first20.push_back("nine") ;
18  first20.push_back("ten") ;
19  first20.push_back("eleven") ;
20  first20.push_back("twelve") ;
21  first20.push_back("thirteen") ;
22  first20.push_back("fourteen") ;
23  first20.push_back("fifteen") ;
24  first20.push_back("sixteen") ;
25  first20.push_back("seventeen") ;
26  first20.push_back("eighteen") ;
27  first20.push_back("nineteen") ;
28    
29  tens.clear() ;
30  tens.reserve(10) ;
31  tens.push_back("zero") ;
32  tens.push_back("ten") ;
33  tens.push_back("twenty") ;
34  tens.push_back("thirty") ;
35  tens.push_back("forty") ;
36  tens.push_back("fifty") ;
37  tens.push_back("sixty") ;
38  tens.push_back("seventy") ;
39  tens.push_back("eighty") ;
40  tens.push_back("ninety") ;
41}
42
43NumToString::~NumToString() {
44  
45}
46
47string
48NumToString::to_string_less_than_1000( int num ) const {
49
50  string res = "" ;
51  // convert the first two digit
52  int tmp = num%100 ;
53  if ( tmp < 20 ) {
54    res = first20[tmp] ;
55  } else {
56    res = tens[tmp/10] ;
57    if ( (tmp%10) != 0 ) res += "-" + first20[tmp%10] ;
58  }
59  
60  // convert hundreds
61  num /= 100 ;
62  tmp = num%10 ;
63  if ( tmp > 0 ) {
64    if ( res.length() > 0 ) res = first20[tmp]+"-hundred-"+res ;
65    else                    res = first20[tmp]+"-hundred" ;
66  }
67  return res ;
68
69}
70
71
72string
73NumToString::to_string( int num ) const {
74  string res = to_string_less_than_1000( num ) ;
75
76  // convert thousand
77  string res1 = to_string_less_than_1000( num/1000 ) ;
78  if ( res1.length() > 0 ) {
79    if ( res.length() > 0 ) res = res1+"-thousand-"+res ;
80    else                    res = res1+"-thousand" ;
81  }
82
83  // convert millions
84  res1 = to_string_less_than_1000( num/1000000 ) ;
85  if ( res1.length() > 0 ) {
86    if ( res.length() > 0 ) res = res1+"-million-"+res ;
87    else                    res = res1+"-million" ;
88  }
89
90  // convert billion
91  res1 = to_string_less_than_1000( num/1000000000 ) ;
92  if ( res1.length() > 0 ) {
93    if ( res.length() > 0 ) res = res1+"-billion-"+res ;
94    else                    res = res1+"-billion" ;
95  }
96
97  return res ;
98}

File test_num_to_string.cc

:open:
 1#include "num_to_string.hh"
 2#include <iostream>
 3
 4using namespace std ;
 5
 6int
 7main() {
 8  NumToString nts ;
 9  
10  for ( int i = 1000000 ; i < 1000000+333 ; ++i )
11    cout << i << " --> " << nts.to_string(i) << '\n' ;
12    
13}

All the files in one zip file

2014_07_24.zip