2

このプログラムを実装するために使用している完全なコードを次に示します。すべてがコンパイルおよび実行されているように見えますが、find メソッドを実行すると、プログラムが停止したように見え、main.cpp ファイル内の一致する部分文字列を示す最後の行が実行されません。どんな助けでも大歓迎です！

.h ファイル:

#include <iostream>
using namespace std;

class MyString
{
    public:
            MyString();
            MyString(const char *message);
            MyString(const MyString &source);
            ~MyString();
            const void Print() const;
            const int Length() const;
            MyString& operator()(const int index, const char b);
            char& operator()(const int i);

            MyString& operator=(const MyString& rhs);
            bool operator==(const MyString& other) const;
            bool operator!=(const MyString& other) const;
            const MyString operator+(const MyString& rhs) const;
            MyString& operator+=(const MyString& rhs);
            friend ostream& operator<<(ostream& output, const MyString& rhs);
            const int Find(const MyString& other);
            MyString Substring(int start, int length);

    private:
            char *String;
            int Size;


   };

  istream& operator>>(istream& input, MyString& rhs);

.cpp ファイル:

   #include <iostream>
  #include <cstdlib>
  #include "MyString.h"

  using namespace std;

  //default constructor that sets the initial string to the value "Hello World"
 MyString::MyString()
 {
    char temp[] = "Hello World";

    int counter(0);
    while(temp[counter] != '\0')
    {
            counter++;
    }
    Size = counter;
    String = new char [Size];
    for(int i=0; i < Size; i++)
            String[i] = temp[i];

 }

 //alternate constructor that allows for setting of the inital value of the string
 MyString::MyString(const char *message)
{
    int counter(0);
    while(message[counter] != '\0')
    {
            counter++;
    }
    Size = counter;
    String = new char [Size];
    for(int i=0; i < Size; i++)
            String[i] = message[i];
  }

    //copy constructor
  MyString::MyString(const MyString &source)
  {

     int counter(0);
    while(source.String[counter] != '\0')
    {
            counter++;
    }
    Size = counter;
    String = new char[Size];
    for(int i = 0; i < Size; i++)
            String[i] = source.String[i];
  }

 //Deconstructor
 MyString::~MyString()
{
    delete [] String;
 }

//Length() method that reports the length of the string
const int MyString::Length() const
{
    int counter(0);

    while(String[counter] != '\0')
    {
            counter ++;
    }
    return (counter);
 }

/*Parenthesis operator should be overloaded to replace the Set and Get functions of    your previous assignment. Note that both instances should issue exit(1) upon violation of the string array bounaries.
*/
 MyString& MyString::operator()(const int index, const char b)
{
    if(String[index] == '\0')
    {
            exit(1);
    }
    else
    {
            String[index] = b;
    }
}

char& MyString::operator()(const int i)
{
    if(String[i] == '\0')
    {
            exit(1);
    }
    else
    {
            return String[i];
    }
}
 /*Assignment operator (=) which will copy the source string into the destination string. Note that size of the destination needs to be adjusted to be the same as the source.
 */
   MyString& MyString::operator=(const MyString& rhs)
  {
    if(this != &rhs)
    {
            delete [] String;
            String = new char[rhs.Size];
            Size = rhs.Size;

            for(int i = 0; i < rhs.Size+1 ; i++)
            {
                    String[i] = rhs.String[i];
            }
    }

    return *this;
  }
 /*Logical comparison operator (==) that returns true iff the two strings are identical in size and contents.
 */
  bool MyString::operator==(const MyString& other)const
  {
    if(other.Size == this->Size)
    {
            for(int i = 0; i < this->Size+1; i++)
            {
                    if(&other == this)                               

                        return true;
            }
    }
    else
            return false;
    }

 //Negated logical comparison operator (!=) that returns boolean negation of 2
    bool MyString::operator!=(const MyString& other) const
  {
    return !(*this == other);
  }

 //Addition operator (+) that concatenates two strings
 const MyString MyString::operator+(const MyString& rhs) const
 {
    char* tmp = new char[Size + rhs.Size +1];

    for(int i = 0; i < Size; i++)
    {
            tmp[i] = String[i];
    }
    for(int i = 0; i < rhs.Size+1; i++)
    {
            tmp[i+Size] = rhs.String[i];
    }
    MyString result;

    delete [] result.String;
    result.String = tmp;
    result.Size = Size+rhs.Size;

    return result;
 }
 /*Addition/Assigment operator (+=) used in the following fashion: String1 += String2 to operate as String1 = String1 + String2
*/
MyString& MyString::operator+=(const MyString& rhs)
{
    char* tmp = new char[Size + rhs.Size + 1];

    for(int i = 0; i < Size; i++)
    {
            tmp[i] = String[i];
    }        for(int i = 0; i < rhs.Size+1; i++)
    {
            tmp[i+Size] = rhs.String[i];
    }

    delete [] String;
    String = tmp;
    Size += rhs.Size;

    return *this;
 }
 istream& operator>>(istream& input, MyString& rhs)
{
    char* t;
    int size(256);
    t = new char[size];
    input.getline(t,size);

    rhs = MyString(t);
    delete [] t;

    return input;
 }

 ostream& operator<<(ostream& output, const MyString& rhs)
{
    if(rhs.String != '\0')
    {
            output << rhs.String;
    }
    else
    {
            output<<"No String to output\n";
    }

    return output;
 }

  const int MyString::Find(const MyString& other)
 {
       int nfound = -1;

    if(other.Size > Size)
    {
            return nfound;
    }
    int i = 0, j = 0;
    for(i = 0; i < Size; i++)
    {
            for(j = 0; j < other.Size; j++)
            {
                    if( ((i+j) >= Size) || (String[i+j] != other.String[j]) )
                    {
                            break;
                    }

            }

            if(j == other.Size)
            {
                    return i;
            }

    }

    return nfound;
    }
  /*MyString::Substring(start, length). This method returns a substring of the original string that contains the same characters as the original string starting at location start and is as long as length.
 */

 MyString MyString::Substring(int start, int length)
 {
    char* sub;
    sub = new char[length+1];


    while(start != '\0')
    {
            for(int i = start; i < length+1; i++)
            {
                    sub[i] = String[i];
            }
    }
    return MyString(sub);
 }

 //Print() method that prints the string
 const void MyString::Print() const
 {

    for(int i=0; i < Size; i++)
    {
            cout<<String[i];
    }
    cout<<endl;
  }

main.cpp ファイル:

  #include <cstdlib>
  #include <iostream>
 #include "MyString.h"


  using namespace std;

 /*
 *
 */
int main (int argc, char **argv)
{

 MyString String1; // String1 must be defined within the scope

 const MyString ConstString("Target string");          //Test of alternate constructor

  MyString SearchString;  //Test of default constructor that should set "Hello World". W/o ()
 MyString TargetString (String1); //Test of copy constructor


  cout << "Please enter two strings. ";
 cout << "Each string needs to be shorter than 256 characters or terminated by /\n." << endl;
 cout << "The first string will be searched to see whether it contains exactly the second string. " << endl;

  cin >> SearchString >> TargetString; // Test of cascaded string-extraction operator


 if(SearchString.Find(TargetString) == -1) {
      cout << TargetString << " is not in " << SearchString << endl;
   }
   else {
    cout << TargetString << " is in " << SearchString << endl;
    cout << "Details of the hit: " << endl;
    cout << "Starting poisition of the hit: " << SearchString.Find(TargetString) << endl;
    cout << "The matching substring is: " << SearchString.Substring(SearchString.Find(TargetString), TargetString.Length());
  }
 return 0;
}
4

4 に答える 4

3

内側のループの不変条件は、j が 0 と end-2 の間にあることです。したがって、j は end と等しくなることはありません (「一致」条件)。

于 2012-06-14T22:40:45.963 に答える
1

foundロジックに問題があるようです。

あなたのforループは次のように定義されていますfor(int j = 0; j < end -1; j++)

しかし、あなたはテストしますif(j == end)

jendこの for ループでと等しくなることはありません。if ステートメントで実際にテストしようとしているものを検討してください。

于 2012-06-14T22:39:07.223 に答える
0

他の誰もが言ったことに加えて、Substring メソッドには次のコードがあります。

 while(start != '\0')
 {
     for(int i = start; i < length+1; i++)
     {
         sub[i] = String[i];
     }
}

少し時間を取って、while ループのロジックを調べて、「ここで何を達成しようとしているのか、このコードは実際に何をしているのか?」と自問してください。

于 2012-06-16T09:19:14.527 に答える