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What is an undefined reference/unresolved external symbol error and how do I fix it?
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Closed 1 year ago.
cpp
#include <iostream>
#include <stack>
#include <string>
using namespace std;
class Pstring : public string
{
public:
Pstring(string revWrd);
bool isPalindrome(string ip);
};
bool isPalindrome(string revWrd)
{
int test;
int left = 0;
int right = revWrd.size()-1;
int length = left;
while (test != length)
{
test++;
if ((revWrd[left] != revWrd[right]))
return false;
else
return true;
left++;
--right;
}
}
int main()
{
string word;
bool palindrome;
Pstring palindromeTested(word);
cout << "Enter a word or sentence to have it\n";
cout << "reversed and tested if it is a palindrome: ";
getline(cin, word);
palindrome = palindromeTested.isPalindrome(word);
if(palindrome==true)
cout<<"This is a palindrome"<<endl;
else
cout <<"That was not a palindrome";
return 0;
}
i get 2 error codes which are 1 "undefined reference to `Pstring::Pstring(std::__cxx11::basic_string, std::allocator >)'|"
and
2 "undefined reference to `Pstring::isPalindrome(std::__cxx11::basic_string, std::allocator >)'|
The error is because the member functions in the class Pstring are not defined.
The class doesn't seem used effectively, so you should remove that.
Also there are some other errors:
The variable test is used without being initialzed.
return true; is in wrong place, making strings like abcda be judged as palindrome.
#include <iostream>
#include <stack>
#include <string>
using namespace std;
bool isPalindrome(string revWrd)
{
int test = 0; // initialize test
int left = 0;
int right = revWrd.size()-1;
int length = left;
while (test != length)
{
test++;
if ((revWrd[left] != revWrd[right]))
return false;
// else
// don't return here to check all parts of the string
left++;
--right;
}
return true; // return at end of funciton
}
int main()
{
string word;
bool palindrome;
cout << "Enter a word or sentence to have it\n";
cout << "reversed and tested if it is a palindrome: ";
getline(cin, word);
palindrome = isPalindrome(word);
if(palindrome==true)
cout<<"This is a palindrome"<<endl;
else
cout <<"That was not a palindrome";
return 0;
}
Related
So recently i started to getting into stacks ADT in c++ and i am trying to create a small program which the user inserts a string and the output should be in reverse order
But something is going wrong with my code or i am missing something but i cant figure it out
My output so far is that i can insert the string but then it just output the couts "Reverse string" and nothing else
i tried several ways like to change the pop function but nothing changed
Thank you for any help
#include <iostream>
#include <string>
using namespace std;
class ReverseString {
public:
string str[13];
int topStack;
ReverseString() {
topStack = -1;
}
string Push() {
//char item;
string str("");
cout << "Enter a string " << endl;
cin >> str;
for (char ch : str) {
topStack++;
// str[topStack] = item;
return str;
}
}
string Pop() {
string temp= str[topStack];
for (int i = 0; i <= 13; i++) {
str[i] = temp;
//temp = str[i - 1];
cout << "Reverse String: " << str[topStack] << endl;
return temp;
}
}
};
// main function
int main() {
ReverseString str;
str.Push();
str.Pop();
return 0;
}
I am trying to write a code which lists all words used in a text file without repeating. I succeeded to list all the words but I always get repeating ,the if statement line 17 always gives the value of 0.I have no idea why , the words are listed properly in the vector. Any suggestion ?
#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
class reading {
public:
string word;
vector<string> words;
};
int checkifexist(string word) {
reading readingobject;
bool exist = false;
for (int i = 0; i < readingobject.words.size(); i++) {
if (word == readingobject.words[i]) {
exist = true;
break;
}
}
return exist;
}
int main() {
reading readingobject;
ifstream inFile;
inFile.open("Book.txt");
if (inFile.fail()) {
cout << "file didn't open" << endl;
exit(1);
}
readingobject.word.resize(1);
while (!inFile.eof()) {
inFile >> readingobject.word;
if (checkifexist(readingobject.word) == 1)
continue;
cout << readingobject.word << endl;
readingobject.words.push_back(readingobject.word);
}
return 0;
}
Inside of checkifexist(), you are creating a new reading object, whose words vector is empty, so there is nothing for the loop to do, and the function returns 0.
You need to instead pass in the reading object from main() as an input parameter, eg:
#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
class reading {
public:
vector<string> words;
};
bool checkifexist(const reading &readingobject, const string &word)
{
for (size_t i = 0; i < readingobject.words.size(); ++i) {
if (word == readingobject.words[i]) {
return true;
}
}
return false;
/* alternatively:
return (std::find(readingobject.words.begin(), readingobject.words.end(), word) != readingobject.words.end());
*/
}
int main()
{
reading readingobject;
string word;
ifstream inFile;
inFile.open("Book.txt");
if (!inFile) {
cout << "file didn't open" << endl;
return 1;
}
while (inFile >> word) {
if (checkifexist(readingobject, word))
continue;
cout << word << endl;
readingobject.words.push_back(word);
}
return 0;
}
Alternatively, when it comes to tracking unique elements, you can use a std::set instead of a std::vector, eg:
#include <iostream>
#include <fstream>
#include <set>
using namespace std;
class reading {
public:
set<string> words;
};
int main()
{
reading readingobject;
string word;
ifstream inFile;
inFile.open("Book.txt");
if (!inFile) {
cout << "file didn't open" << endl;
return 1;
}
while (inFile >> word) {
if (readingobject.words.insert(word).second)
cout << word << endl;
}
return 0;
}
I want to know how to check if a word is palindrome in struct data type or object whatever you want to call it. I want to read a data from file then I need to check if that type of word that I have read is a palindrome or not. Also i need to reverse order of the words but I did that so do not need any help about that.
Here is the code:
#include <iostream>
#include <fstream>
#include <string>
#include <algorithm>
using namespace std;
struct lettersStr
{
string name;
string object;
};
int main(int argc, char** argv)
{
ifstream letter;
letter.open("letter.txt");
lettersStr things[200];
int numberOfThings= 0;
while(letter >> letter[numberOfThings].name >> letter[numberOfThings].object)
{
numberOfThings++;
}
for (int i = 0; i < numberOfThings; i++)
{
cout << letter[i].name << " " << letter[i].object<< endl;
}
string names;
for (int i = 0; i < numberOfThings; i++)
{
names= things[i].name;
}
for (int i = numberOfThings- 1; i >= 0; i--)
{
cout << things[i].name << endl;
}
bool x = true;
int j = names.length() - 1;
for (int i = 0; i < j; i++,j--)
{
if (things[i].name.at(i) != things[i].name.at(j))
x = false;
if (x)
{
cout << "String is a palindrome ";
}
else
cout << "String is not a palindrome";
}
And here is the cout:
Kayak Audi
Ahmed Golf7
Ahmed
Kayak
String is not a palindrome
String is not a palindrome
I think major problem is this:
for (int i = 0; i < j; i++,j--)
{
if (things[i].name.at(i) != things[i].name.at(j))
x = false;
As you can see it wont cout right way of checking if a word is palindrome or not.
P.S: If this is a stupid question I am sorry, I am a beginner in C++ programming.
Cheers
As already pointed out in the comments, for (int i = 0; i < j; i++,j--) loops though things and the letters of their names simultaneously. You also have to account for cases where you compare a lower and an upper case letter such as the 'K' and 'k' at the beginning and end of 'Kayak'. You can use std::tolower for this.
Here is an example (live demo):
#include <iostream>
#include <fstream>
#include <string>
#include <algorithm>
#include <vector>
using namespace std;
bool is_palindrome(std::string name)
{
if (name.empty())
return false;
// As has been pointed out, you can also use std::equal.
// However, this is closer to your original approach.
for (unsigned int i = 0, j = name.length()-1; i < j; i++,j--)
{
if (std::tolower(name.at(i)) != std::tolower(name.at(j)))
return false;
}
return true;
}
struct lettersStr
{
string name;
string object;
};
int main(int argc, char** argv)
{
std::vector<lettersStr> vec = {lettersStr{"Kayak","Boat"},lettersStr{"Audi","Car"}};
for (const auto &obj : vec)
if (is_palindrome(obj.name))
std::cout << obj.name << " is a palindrome" << std::endl;
else
std::cout << obj.name << " isn't a palindrome" << std::endl;
}
It gives the output:
Kayak is a palindrome
Audi isn't a palindrome
Beginner C++ student here, first ever programming class. I am trying to put together a program that will identify if a string is all lower case or not. I got as far as the code below. However, I need to account for spaces " ". If there is a space in the string that is input by the user, the program is suppose to return that it is not all lower case. Example:
input: abc def
return: The string is not lower case.
Would any of you ever so kindly advise what would be the best way to account for this in the code below?
NOTE: I know I have 'included' some extra header files, but that is because this is going to be part of another program and this is just an excerpt to get things running.
Thank you so very much all!!
#include <fstream>
#include <iostream>
#include <string>
#include <cstdlib>
#include <algorithm>
#include <cctype>
#include <iomanip>
using namespace std;
bool die(const string & msg);
bool allLower(const string & l);
int main() {
string l;
cout << "\nEnter a string (all lower case?): ";
cin >> l;
if (allLower(l) == true)
{
cout << "The string is lower case." << endl;
}
else
{
cout << "The string is not lower case." << endl;
}
}
bool allLower(const string & l) {
struct IsUpper {
bool operator()(int value) {
return ::isupper((unsigned char)value);
}
};
return std::find_if(l.begin(), l.end(), IsUpper()) == l.end();
}
bool die(const string & msg){
cout << "Fatal error: " << msg << endl;
exit(EXIT_FAILURE);
}
You could use a good old fashion for-loop.
bool allLower(const std::string & l)
{
for(unsigned int i = 0; i < l.size(); i++)
{
if(l[i] == ' ')
{
return false;
}
else if(isalpha(l[i]))
{
if(isupper(l[i]))
return false;
}
}
return true;
}
Note that if you feed it in something like "2" it will return true. You could add a final else statement that returns false if you so desire.
You can check to see if a character is alphabetic using the function std::isalpha() prior to using std::isupper() or std::islower() to checking whether all letters within your string are uppercase/lowercase, etc
A range-based for loop would be clearer than indices IMO
bool allLower(const std::string &l)
{
for (auto c : l)
{
if ((c == ' ') ||
(std::isalpha(c) && std::isupper(c)))
{
return false;
}
}
return true;
}
I'm creating a program that is meant to sort genome strings, and I've run into an issue with the output.
Code:
#include <iostream>
#include <string>
#include <cctype>
#include <cmath>
#include <algorithm>
using namespace std;
int main()
{
string genome;
cout << "Enter a genome string: ";
cin >> genome;
int geneCounter = 0;
while(!genome.empty()) //enters loop if strings not empty
{
if(genome.find("ATG") == string::npos)
{
if(geneCounter == 0)
{
cout << "No gene is found";
genome.clear();
}
return 0;
}
else
{
int startGene = genome.find("ATG");
int endGene = min(min(genome.find("TAG"), genome.find("TAA")), genome.find("TGA"));
string currentGene = genome.substr(startGene + 3, endGene - (startGene +3));
if((currentGene.length() % 3) == 0)
{
geneCounter += 3;
cout << currentGene <<endl;
}
endGene += 3;
genome.erase(0, endGene);
cout << genome;
}
}
return 0;
}
The code itself runs fine, it displays "No gene is found" correctly and doesn't stick me in a loop of not closing.
However, the string I'm being asked to test it with (TTATGTTTTAAGGATGGGGCGTTAGTT), does not output the correct results.
Whenever I input the string I get the following:
TTT
GGATGGGGCGTTAGTTGGGCGT
TT
When I should be getting:
TTT
GGGGCGT
I feel like I'm missing something very simple, any help would be appreciated.