Deleting Duplicate chars from a string - c++

Question

Hello I'm kind of new to coding and I am writing a code that deletes any duplicate characters on a string. Let's say the input string was ABBA, then the output should be "empty" since all of the duplicates were deleted. Another example would be if the input string was KKCCD, then the output should be "D" as the code would remove the K and C duplicates. The problem with my code is that when I type KKCCD, it returns KCD and it doesnt delete the duplicates entirely. Also if I we're to type "AA" the result comes back as "A" instead of "Empty". Any help in fixing my code will be much apreciated. Thanks.
include
#include <string.h>
using namespace std;
string deduplicate(string input){
int i;
int x;
int len= input.length();
string outputStr;
string strEmpty = "Empty";
if (input.length() == 1)
{return input;}
for(i = 0; i<len;i++){
for(x = i+1; x<len; x++){
if(input[i] == input[x]){
input.erase(x,1);
x--;}
}
len = input.length();
}
return outputStr = input;
if (input.length() == 0)
{return strEmpty;}
return outputStr = input;
}
int main()
{
string input;
cout << "Enter a string: " << endl;
cin >> input;
cout << deduplicate(input);
return 0;
}

Answer 1

Change your duplicate function to this
string deduplicate(string input){
int i;
int x;
int len= input.length();
string outputStr;
string strEmpty = "Empty";
if (input.length() == 1)
{return input;}
for(i = 0; i<len;i++){
for(x = i+1; x<input.length(); x++){ // This line
if(input[i] == input[x]){
input.erase(x,1);
input.erase(i,1); // and this line
x--;
}
}
len = input.length();
}
return outputStr = input;
if (input.length() == 0)
{return strEmpty;}
return outputStr = input;
}
You did delete the duplicate character but not original, so the second erase statement does it.

Answer 2

You are deleting the duplicate you find, but you never delete the original character. The most efficient way to achieve your goal is to use STL algorithms. You might want to check out this link: Remove all duplicate characters from a string (STL)

Answer 3

Generally speaking I do not think if that is a good idea to delete characters from a string you are iterating. It would be much better and cleaner to construct your output instead:
#include <string>
#include <iostream>
using namespace std;
string deduplicate(string input) {
string outputStr;
if (input.length() == 1) {
return input;
}
for ( int i = 0; i < input.length(); i++ ) {
// try to find character at the rest of the string
if ( input.find( input[i], i+1 ) == string::npos ) {
// try to find character in the front
if ( ( i > 0 ) && ( input.rfind( input[i], i-1 ) == string::npos ) ) {
outputStr += input[i];
}
}
}
return outputStr;
}
int main()
{
string input;
cout << "Enter a string: " << endl;
cin >> input;
cout << deduplicate(input) << endl;
return 0;
}

Answer 4

Here is a "brute force" implementation.
string deduplicate(string str)
{
size_t l = str.length();
bool bFound = false;
char character = 0;
for (int i = 0; i < l; i++)
{
character = str[i];
while (true)
{
size_t next = str.rfind(character);
if (next != std::string::npos)
{
if (bFound || (!bFound && next != i))
{
str.erase(next, 1);
bFound = true;
l--;
}
}
if (next == i)
{
if (bFound == true)
{
i--;
}
bFound = false;
break;
}
}
}
return str;
}