Delete repeated characters from a random word - c++

Question

I'm making a class to delete repeated character from a random word. For example if the input is "aabbccddeeff", it should output "abcdef". However my output contains strange characters after "abcdef". The main.cpp file already exists as the requirements for creating the class. Please see the following codes:
main.ccp
#include <iostream>
#include "repeatdeletion.h"
using namespace std;
int main()
{
char* noRepeats;
int length;
string s;
cout<<"Enter a random word with repeating characters: ";
cin>>s;
RepeatDeletion d;
length=s.length();
noRepeats=d.deleteRepeats(s, length);
cout<<"Your word without any repeating characters: ";
for (int k=0; k<length; k++){
cout<<noRepeats[k];
}
cout<<endl;
delete [] noRepeats;
noRepeats=NULL;
return 0;
}
repeatdeletion.h
#ifndef REPEATDELETION_H
#define REPEATDELETION_H
#include <iostream>
using namespace std;
class RepeatDeletion
{
char* c;
char arr[128]={};
bool repeated;
bool isRepeated(char);
public:
RepeatDeletion();
~RepeatDeletion();
char* deleteRepeats(string, int);
};
#endif // REPEATDELETION_H
repeatdeletion.cpp
#include "repeatdeletion.h"
RepeatDeletion::RepeatDeletion()
{
repeated=false;
}
RepeatDeletion::~RepeatDeletion()
{
delete [] c;
c=NULL;
}
bool RepeatDeletion::isRepeated(char c){
bool repeated=false;
if (arr[c]>=1){
repeated=true;
arr[c]++;
}else{
arr[c]++;
}
return repeated;
}
char* RepeatDeletion::deleteRepeats(string str, int len){
c=new char[len];
int j=0;
for (int i=0; i<len; i++){
if (isRepeated(str[i])==false){
c[j]=str[i];
j++;
}
}
return c;
}

Answer 1

Your return character array is not null terminated.
The length function of string does not include \0.
You have two choices
Add null at the end of returned character array, and std::cout the char array directly (instead of char by char)
Output the final length of your char array, and use that as range to print it char by char

Answer 2

Your printing loop loops using the old and unmodified string length. That means you will go outside the characters you added to memory returned by deleteRepeats.
The easiest solution to handle this is to terminate the data as a proper string, and check for the terminator in the loop.

Answer 3

If you want to use a C-string array, they have a null terminator at the end. That means you'll want to (in deleteRepeats) define your character array one character larger than the length:
c=new char[len+1];
And, after the for loop, ensure you put that null terminator in:
c[j] = '\0';
Then, in your calling function, you can just do:
cout << noRepeats;
Even if you don't want to use C strings, you'll need to communicate the new length back to the caller somehow (currently, you're using the original length). The easiest way to do that is (IMNSHO) still using a C-style string and using strlen to get the new length (a).
Otherwise, you're going to need something like a reference parameter for the new length, populated by the function and used by the caller.
(a) But I'd suggest rethinking the way you do things. If you want to be a C++ coder, be a C++ coder. In other words, use std::string for strings since it avoids the vast majority of problems people seem to have with C strings.

Answer 4

That's because in your code you write the following:
cout<<"Your word without any repeating characters: ";
for (int k=0; k<length; k++){
cout<<noRepeats[k];
}
cout<<endl;
Here, length refers to the length of the original string (which you, by the way shouldn't pass to your deleteRepeats method). I would suggest you make deleteRepeats return a string and write something like this:
std::string noRepeats = d.deleteRepeats(s);
std::cout << "Your word without any repeating characters: ";
std::cout << noRepeats << std::endl;
C-style string (char *, if you insist) follow the convention that the last character is '\0', indicating that the string ends. You could also change deleteRepeats by appending '\0', i.e.
char* RepeatDeletion::deleteRepeats(string str){
c = new char[str.size() + 1];
int j = 0;
for (int i = 0; i < str.size(); i++){
if(isRepeated(str[i]) == false){
c[j] = str[i];
j++;
}
}
c[j] = '\0';
return c;
}
and in your main
std::cout << noRepeats << std::endl;
instead of the for loop. But really, you should use std::string, and if possible not mix it with char *. Hope that helps.

Answer 5

for(k=0;k<length;k++)
Here length should be the exact length of noRepeats, but not of s
so :
char* RepeatDeletion::deleteRepeats(string str, int len)
should return the length-after too

Answer 6

use std::unique it does what you want:
std::string s{};
std::cin>>s;
auto it = std::unique(std::begin(s), std::end(s));
s.resize(std::distance(std::begin(s),it));
std::cout << s;
the way it works is to go through the range begin to end and move all the remaining elements forward if the current element is equal to the next. It returns the position of the end of the new string (it in this example) but does not actually shorten the string so on the next line we shorten the string to the length equal to the distance of begin() to it.
see live at http://ideone.com/0CeaHW