C++ (Reverse string)

Question

minghags 0 Junior Poster in Training

12 Years Ago

Hello! Im having trouble with reversing string in this program:

#include <iostream>
#include <string>
using namespace std;
int numChars(string besedilo[])
{
    int znaki=0;
    int vrstica=0;
    for(int a=0;a<10;a++)
    {
        vrstica=besedilo[a].length();
        znaki=znaki+vrstica;
    }
    return znaki;
}
int numWords(string besedilo[])
{
    int besede=0;
    string vrsta;
    for(int a=0;a<1;a++)
    {
        vrsta=besedilo[a];
        for(int b=0;b<besedilo[a].length();b++)
        {
            if(vrsta[b]==' ' || vrsta[b]=='\n')
            {
                besede++;
            }
        }
        besede++;
    }
    return besede;
}

int reverseString(string stavek)
{
    std::string str = stavek;

    std::string rstr = str;
    std::reverse(rstr.begin(), rstr.end());
    std::cout << rstr << std::endl;
    
}

int main()
{
    string vrstica[10];
    string ime;
    int meni;
    cout<<"Vnesi besedilo: "<<endl<<"---------------"<<endl<<endl;
    for(int a=0;a<1;a++)
    {
        getline(cin,vrstica[a]);
    }
        
    cout<<endl<<"-----------------------"<<endl;
    do
    {
        cout<<"+++++++++++++++++++++++++++++++++++++++++++++++++"<<endl;
        cout<<"  MENU                                          +"<<endl;
        cout<<"1. Izpise stevilo vnesenih znakov               +"<<endl;
        cout<<"2. Izpise stevilo vnesenih besed                +"<<endl;
        cout<<"3. Obrne niz                                    +"<<endl;
        cout<<"0. Izhod                                        +"<<endl;
        cout<<"+++++++++++++++++++++++++++++++++++++++++++++++++"<<endl<<endl;
        cin>>meni;
        if(meni==1)
        {
            cout<<"Vneseno je bilo "<<numChars(vrstica)<<" znakov!"<<endl;
        }
        if(meni==2)
        {
            cout<<endl<<"Vneseno je bilo "<<numWords(vrstica)<<" besed!"<<endl;
        }
        if(meni==3)
        {            
            cout<<reverseString(vrstica);
        }
    }
    while(meni!=0);
    return 0;
}

Can anyone help me with this problem? Thanks.

c++

4 Contributors
14 Replies
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Latest Post 12 Years Ago Latest Post by stereomatching

All 14 Replies

thines01 401 Postaholic

12 Years Ago

Did you see this?:
http://www.daniweb.com/software-development/cpp/code/216820/968600#post968600

deceptikon 1,790 Code Sniper

12 Years Ago

You need to include the algorithm header for std::reverse(). You're also trying to pass an array of strings to reverseString() when it only accepts a single string object.

deceptikon 1,790 Code Sniper

12 Years Ago

Now reverseString() doesn't do any reversing. All it does is make a copy of strings in the array and print them as-is...

stereomatching 17 Posting Whiz in Training

12 Years Ago

compile by vc2010, coding style of C++11?

#include<algorithm> //for std::for_each, std::reverse and std::copy
#include<array> //for std::array
#include<iostream> //for std::cout, std::cin.get
#include<iterator> //for std::ostream_iterator
#include<string>

template<typename T>
void reverseString(T &value)
{  
  std::for_each(value.begin(), value.end(),
  [](std::string &fir)
  {
    std::reverse(fir.begin(), fir.end());
  });
}

int main()
{    
  std::array<std::string, 3> value = {"one", "two", "three"};
  reverseString(value);
  std::copy(value.begin(), value.end(), std::ostream_iterator<std::string>(std::cout,"\n"))；
  std::cin.get();

  return 0;
}

compile by vc2010, coding style of C++98?

#include<algorithm>
#include<iostream>
#include<string>

//I don't know how to deduce the number of the element at compile time
//without passing a parameter "num", please tell me how to
//do it if you know, thanks
void reverseString(std::string value[], size_t num)
{
  for(size_t i = 0; i != num; ++i)
    std::reverse(value[i].begin(), value[i].end() );
}

int main()
{    
  std::string value[] = {"one", "two", "three"};
  reverseString(value, sizeof(value)/ sizeof(*value) );
  std::copy(value, value + 3, std::ostream_iterator<std::string>(std::cout,"\n"))；
  std::cin.get();

  return 0;  
}

the implementation of std::reverse are quite simple
I only post the one with random access iterator(a smart pointer which similar to pointer)

template<typename RandomItr>
void Reverse(RandomItr begin, RandomItr end)
{
  while(begin < end)
  {
    std::iter_swap(begin, --end);
    ++begin;
  }
}

Edited 12 Years Ago by stereomatching because: n/a

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minghags 0 Junior Poster in Training · Answer 1 · 2012-02-27T20:22:00+00:00

I tried like this and no luck :(

#include <iostream>
#include <string>
using namespace std;
int numChars(string besedilo[])
{
    int znaki=0;
    int vrstica=0;
    for(int a=0;a<10;a++)
    {
        vrstica=besedilo[a].length();
        znaki=znaki+vrstica;
    }
    return znaki;
}
int numWords(string besedilo[])
{
    int besede=0;
    string vrsta;
    for(int a=0;a<1;a++)
    {
        vrsta=besedilo[a];
        for(int b=0;b<besedilo[a].length();b++)
        {
            if(vrsta[b]==' ' || vrsta[b]=='\n')
            {
                besede++;
            }
        }
        besede++;
    }
    return besede;
}

int reverseString(string besedilo[])
{
    char temp1[5];
    
    for (int i = 5; i > -1; i--)
    {
        string temp1 = besedilo[i];
        besedilo[i] = temp1;
        cout<<besedilo[i];
    }
    cout<<endl;
    
}

int main()
{
    string vrstica[10];
    string besedilo;
    int meni;
    cout<<"Vnesi besedilo: "<<endl<<"---------------"<<endl<<endl;
    for(int a=0;a<1;a++)
    {
        getline(cin,vrstica[a]);
    }
        
    cout<<endl<<"-----------------------"<<endl;
    do
    {
        cout<<"+++++++++++++++++++++++++++++++++++++++++++++++++"<<endl;
        cout<<"  MENU                                          +"<<endl;
        cout<<"1. Izpise stevilo vnesenih znakov               +"<<endl;
        cout<<"2. Izpise stevilo vnesenih besed                +"<<endl;
        cout<<"3. Obrne niz                                    +"<<endl;
        cout<<"0. Izhod                                        +"<<endl;
        cout<<"+++++++++++++++++++++++++++++++++++++++++++++++++"<<endl<<endl;
        cin>>meni;
                
        if(meni==1)
        {
            cout<<"Vneseno je bilo "<<numChars(vrstica)<<" znakov!"<<endl;
        }
        if(meni==2)
        {
            cout<<endl<<"Vneseno je bilo "<<numWords(vrstica)<<" besed!"<<endl;
        }
        if(meni==3)
        {         
            cout<<endl<<reverseString(vrstica)<<endl;
        }
    }
    while(meni!=0);
    return 0;
}

minghags 0 Junior Poster in Training · Answer 2 · 2012-02-27T20:33:38+00:00

Can you give me any pointers please? I can't figure it out...

deceptikon 1,790 Code Sniper Team Colleague Featured Poster · Answer 3 · 2012-02-27T20:50:28+00:00

Replace reverseString() in your original code with this:

int reverseString(string a[])
{
    for (int i = 0; i < 1; i++)
    {
        std::string rstr = a[i];
        std::reverse(rstr.begin(), rstr.end());
        std::cout << rstr << std::endl;
    }
}

I'd offer other suggestions, but I don't want to overwhelm you.

stereomatching 17 Posting Whiz in Training · Answer 4 · 2012-02-28T12:06:10+00:00

another solution

#include<algorithm>
#include<iostream>
#include<iterator>
#include<string>

template<typename ForwardItr>
void reverseString(ForwardItr begin, ForwardItr end)
{
  while(begin != end)
  {
    std::reverse(begin->begin(), begin->end());
    ++begin;
  }
}

int main()
{
  std::string value[] = {"one", "two", "three"};
  enum {Size = sizeof(value)/ sizeof(*value)};
  reverseString(value, value +  Size);
  std::copy(value, value + Size, std::ostream_iterator<std::string>(std::cout,"\n"))；
  std::cin.get();

  return 0;
}

you could place your std::string into std::vector or std::list either

#include<algorithm>
#include<iostream>
#include<iterator>
#include<string>
#include<vector>

template<typename ForwardItr>
void reverseString(ForwardItr begin, ForwardItr end)
{
  while(begin != end)
  {
    std::reverse(begin->begin(), begin->end());
    ++begin;
  }
}

int main()
{
  char const *str[] = {"one", "two", "three"};
  std::vector<std::string> value(str, str + sizeof(str) / sizeof(*str) );
  reverseString(value.begin(), value.end());
  std::copy(value.begin(), value.end(), std::ostream_iterator<std::string>(std::cout,"\n"))；
  std::cin.get();

  return 0;
}

minghags 0 Junior Poster in Training · Answer 5 · 2012-02-28T18:29:10+00:00

Thanks everyone... It works now... really thanks again everyone...

Now that i don't open new topic I will ask here:

I have to count how many c,s,z are there in that array. I did it like this and i can't figure it out... Thanks again for help...

#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
int numChars(string besedilo[])
{
    int znaki=0;
    int vrstica=0;
    for(int a=0;a<10;a++)
    {
        vrstica=besedilo[a].length();
        znaki=znaki+vrstica;
    }
    return znaki;
}
int numWords(string besedilo[])
{
    int besede=0;
    string vrsta;
    for(int a=0;a<1;a++)
    {
        vrsta=besedilo[a];
        for(int b=0;b<besedilo[a].length();b++)
        {
            if(vrsta[b]==' ' || vrsta[b]=='\n')
            {
                besede++;
            }
        }
        besede++;
    }
    return besede;
}

int reverseString(string a[])
{
    for (int i = 0; i < 1; i++)
    {
        string rstr = a[i];
        reverse(rstr.begin(), rstr.end());
        cout << rstr << endl;
    }
}

int countChar( char * str , char ch )
{
    int countChar = 0;
    
    for ( int i = 0; str[i] != '\0'; i++)
    {
        if ( str[i] == ch )
            countChar = countChar + 1;
    }
    
    return countChar;
}

int main()
{
    string vrstica[10];
    string ime;
    int meni;
    cout<<"Vnesi besedilo: ";
    cout<<endl<<"-----------------------"<<endl;
    for(int a=0;a<1;a++)
    {
        getline(cin,vrstica[a]);
    }
    
    cout<<"-----------------------"<<endl;
    do
    {
        cout<<"+++++++++++++++++++++++++++++++++++++++++++++++++"<<endl;
        cout<<"+    MENU                                       +"<<endl;
        cout<<"+ 1. Izpise stevilo vnesenih znakov             +"<<endl;
        cout<<"+ 2. Izpise stevilo vnesenih besed              +"<<endl;
        cout<<"+ 3. Obrne niz                                  +"<<endl;
        cout<<"+ 4. Prešteje število sičnikov                  +"<<endl;
        cout<<"+ 0. Izhod                                      +"<<endl;
        cout<<"+++++++++++++++++++++++++++++++++++++++++++++++++"<<endl<<endl;
        cin>>meni;
        if(meni==1)
        {
            cout<<"Stevilo znakov: "<<numChars(vrstica)<<endl;
        }
        if(meni==2)
        {
            cout<<endl<<"Stevilo besed: "<<numWords(vrstica)<<endl;
        }
        if(meni==3)
        {            
            cout<<reverseString(vrstica);
        }
        if(meni==4)
        {
            cout << countChar( vrstica , 's' ) << endl;
        }
    }
    while(meni!=0);
    return 0;
}

In this I "did" it for s only...

Thanks again

stereomatching 17 Posting Whiz in Training · Answer 6 · 2012-02-28T21:06:36+00:00

I have to count how many c,s,z are there in that array. I did it like this and i can't figure it out... Thanks again for help...

you mean your countChar has some problem?
Your logics looks good for me, but you have to pass the std::string like this

size_t countChar( vrstica.c_str() , 's' );

and change the interface to

size_t countChar( char const *str , char ch );

besides, you don't need to pass the string by array and write a for loop
you could just do it like this

void reverseString(string const &a)
{    
    string rstr = a;
    reverse(rstr.begin(), rstr.end());
    cout << rstr << endl;    
}

There are many ways to do the same job, you could try another solutions if you like
example : make the codes become shorter and save a temporary variable i

size_t countChar( char const *str , char ch )
{
    size_t countChar = 0;

    //generally speaking, postfix++ is not a good idea, but it
    //is ok for primitive types like char
    while(*str) if(*str++ == ch) countChar += 1;          

    return countChar;
}

you could solve this problem by stl too

template<typename ForwardItr>
size_t countChar( ForwardItr begin , ForwardItr end, char ch)
{
  size_t sum = 0;  
  std::for_each(begin, end, [&](char fir){ if(fir == ch) ++sum;} );

  return sum;
}

minghags 0 Junior Poster in Training · Answer 7 · 2012-02-28T21:17:20+00:00

I did it like this and it works, but there is a problem, one input is string and one an array... How can i fix it, that i wouldn't have to type input twice?

Code:

#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
int numChars(string besedilo[])
{
    int znaki=0;
    int vrstica=0;
    for(int a=0;a<10;a++)
    {
        vrstica=besedilo[a].length();
        znaki=znaki+vrstica;
    }
    return znaki;
}
int numWords(string besedilo[])
{
    int besede=0;
    string vrsta;
    for(int a=0;a<1;a++)
    {
        vrsta=besedilo[a];
        for(int b=0;b<besedilo[a].length();b++)
        {
            if(vrsta[b]==' ' || vrsta[b]=='\n')
            {
                besede++;
            }
        }
        besede++;
    }
    return besede;
}

int reverseString(string a[])
{
    for (int i = 0; i < 1; i++)
    {
        string rstr = a[i];
        reverse(rstr.begin(), rstr.end());
        cout << rstr << endl;
    }
}

int numZ( string str )
{
    int countChar = 0;
    
    for (int i = 0; str[i] != '\0'; i++)
    {
        if ( str[i] == 'z' )
            countChar++;
    }
    
    return countChar;
}

int numS( string str )
{
    int countChar = 0;
    
    for (int i = 0; str[i] != '\0'; i++)
    {
        if ( str[i] == 's' )
            countChar++;
    }
    
    return countChar;
}

int numC( string str )
{
    int countChar = 0;
    
    for (int i = 0; str[i] != '\0'; i++)
    {
        if ( str[i] == 'c' )
            countChar++;
    }
    
    return countChar;
}

int main()
{
    string vrstica[10];
    string ime;
    string besedilo;
    int meni;
    cout<<"Vnesi besedilo: ";
    cout<<endl<<"-----------------------"<<endl;
    for(int a=0;a<1;a++)
    {
        cin >> vrstica[a];
    }
    cin >> besedilo;
    
    cout<<"-----------------------"<<endl;
    do
    {
        cout<<"+++++++++++++++++++++++++++++++++++++++++++++++++"<<endl;
        cout<<"+    MENU                                       +"<<endl;
        cout<<"+ 1. Izpise stevilo vnesenih znakov             +"<<endl;
        cout<<"+ 2. Izpise stevilo vnesenih besed              +"<<endl;
        cout<<"+ 3. Obrne niz                                  +"<<endl;
        cout<<"+ 4. Prešteje število sičnikov                  +"<<endl;
        cout<<"+ 5. Izbris vejic                               +"<<endl;
        cout<<"+ 0. Izhod                                      +"<<endl;
        cout<<"+++++++++++++++++++++++++++++++++++++++++++++++++"<<endl<<endl;
        cin>>meni;
        if(meni==1)
        {
            cout<<"Stevilo znakov: "<<numChars(vrstica)<<endl;
        }
        if(meni==2)
        {
            cout<<endl<<"Stevilo besed: "<<numWords(vrstica)<<endl;
        }
        if(meni==3)
        {            
            cout<<reverseString(vrstica);
        }
        if(meni==4)
        {
            cout << "Stevilo S-ov: " << numS(besedilo) << endl;  
            cout << "Stevilo C-jev: " << numC(besedilo) << endl; 
            cout << "Stevilo Z-jev: " << numZ(besedilo) << endl; 
        }
    }
    while(meni!=0);
    return 0;
}

Thanks in advance...

stereomatching 17 Posting Whiz in Training · Answer 8 · 2012-02-28T21:40:52+00:00

I don't really get your question
you could save all of the string into a vector rather
than save them into an old style array
Then iterate through all of the string in the vector

//don't pass by value but pass by reference
//remember to add const if you don't want the str to be changed
int numS( string str )
{
    int countChar = 0;
    
    for (int i = 0; str[i] != '\0'; i++)
    {
        if ( str[i] == 's' )
            countChar++;
    }
    
    return countChar;
}

you could make your life easier by template

template<char ch>
size_t num( std::string const &str )
{
    int countChar = 0;

    for (int i = 0; str[i] != '\0'; i++)
    {
        if ( str[i] == ch )
            countChar++;
    }

    return countChar;
}

typedef num<'z'> numZ;
typedef num<'s'> numS;
typedef num<'c'> numC;

I don't know why are you want to design something like numA, numZ and so on
would it better than countChar?

minghags 0 Junior Poster in Training · Answer 9 · 2012-02-28T22:06:15+00:00

I did it with your help! Really thanks.

Just one more thing and it is the last really... I want to create function that moves chars for one spot, for example a -> b, b -> d ... is it possible to do that without an array?

Code looks now like that:

#include <iostream>
#include <string>
#include <algorithm>
using namespace std;

int numChars(string besedilo);
int numWords(string besedilo);
int reverseString(string besedilo);
int numC( string str );
int numZ( string str );
int numS( string str );
void removeDots(string besedilo);

int numChars(string besedilo)
{
    int znaki=0;
    int vrstica=0;

        vrstica=besedilo.length();
        znaki=znaki+vrstica;
    
    return znaki;
}
int numWords(string besedilo)
{
    int besede=0;
    string vrsta;
    
        vrsta=besedilo;
        for(int b=0;b<besedilo.length();b++)
        {
            if(vrsta[b]==' ' || vrsta[b]=='\n')
            {
                besede++;
            }
        }
        besede++;
    
    return besede;
}

int reverseString(string besedilo)
{
        string reverseBesedilo = besedilo;
        reverse(reverseBesedilo.begin(), reverseBesedilo.end());
        cout << reverseBesedilo << endl;
}

int numZ( string str )
{
    int countChar = 0;
    
    for (int i = 0; str[i] != '\0'; i++)
    {
        if ( str[i] == 'z' )
            countChar++;
    }
    
    return countChar;
}

int numS( string str )
{
    int countChar = 0;
    
    for (int i = 0; str[i] != '\0'; i++)
    {
        if ( str[i] == 's' )
            countChar++;
    }
    
    return countChar;
}

int numC( string str )
{
    int countChar = 0;
    
    for (int i = 0; str[i] != '\0'; i++)
    {
        if ( str[i] == 'c' )
            countChar++;
    }
    
    return countChar;
}

void removeDots(string besedilo)
{
    for(int i = besedilo.find(",", 0); i != string::npos; i = besedilo.find(",", i))
    {
        besedilo.erase(i,1);
        i++;
    }
    for(int i = besedilo.find(".", 0); i != string::npos; i = besedilo.find(".", i))
    {
        besedilo.erase(i,1);
        i++;
    }
    for(int i = besedilo.find("!", 0); i != string::npos; i = besedilo.find("!", i))
    {
        besedilo.erase(i,1);
        i++;
    }
    for(int i = besedilo.find(":", 0); i != string::npos; i = besedilo.find(":", i))
    {
        besedilo.erase(i,1);
        i++;
    }
    for(int i = besedilo.find(";", 0); i != string::npos; i = besedilo.find(";", i))
    {
        besedilo.erase(i,1);
        i++;
    }
    for(int i = besedilo.find("-", 0); i != string::npos; i = besedilo.find("-", i))
    {
        besedilo.erase(i,1);
        i++;
    }
    cout<<besedilo<<endl;
}

int main()
{
    string vrstica;
    string ime;
    int meni;
    
    cout<<"Vnesi besedilo: ";
    
    cout<<endl<<"-----------------------"<<endl;

        getline(cin,vrstica);
    
    cout<<"-----------------------"<<endl;
    
    do
    {
        cout<<"+++++++++++++++++++++++++++++++++++++++++++++++++"<<endl;
        cout<<"+    MENI:                                      +"<<endl;
        cout<<"+ 1. Izpise stevilo vnesenih znakov             +"<<endl;
        cout<<"+ 2. Izpise stevilo vnesenih besed              +"<<endl;
        cout<<"+ 3. Obrne niz                                  +"<<endl;
        cout<<"+ 4. Prešteje število sičnikov                  +"<<endl;
        cout<<"+ 5. Izbriše ločila                             +"<<endl;
        cout<<"+ 0. Izhod                                      +"<<endl;
        cout<<"+++++++++++++++++++++++++++++++++++++++++++++++++"<<endl<<endl;
        cin>>meni;
        if(meni==1)
        {
            cout<<"Stevilo znakov: "<<numChars(vrstica)<<endl;
        }
        if(meni==2)
        {
            cout<<endl<<"Stevilo besed: "<<numWords(vrstica)<<endl;
        }
        if(meni==3)
        {            
            cout<<reverseString(vrstica);
        }
        if(meni==4)
        {
            cout << "Stevilo S-ov: " << numS(vrstica) << endl;  
            cout << "Stevilo C-jev: " << numC(vrstica) << endl; 
            cout << "Stevilo Z-jev: " << numZ(vrstica) << endl; 
        }
        if(meni==5)
        {
            removeDots(vrstica);
        }
    }
    while(meni!=0);
    return 0;
}

stereomatching 17 Posting Whiz in Training · Answer 10 · 2012-02-29T21:55:06+00:00

I want to create function that moves chars for one spot, for example a -> b, b -> d ... is it possible to do that without an array?

yes, you could do it by list, deque or hash table, but array would be the best choice
in most of the cases.

C++ (Reverse string)

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