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PONeed help with copy constructor for very basic implementation of singly linked lists
 

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  1. PONeed help with copy constructor for very basic implementation of singly linked lists
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    <p>Last week, we created a program that manages sets of strings, using classes and vectors. I was able to complete this 100%. This week, we have to replace the vector we used to store strings in our class with simple singly linked lists. </p> <p>The function basically allows users to declare sets of strings that are empty, and sets with only one element. In the main file, there is a vector whose elements are a struct that contain setName and strSet (class).</p> <p>HERE IS MY PROBLEM: It deals with the copy constructor of the class. When I remove/comment out the copy constructor, I can declare as many empty or single sets as I want, and output their values without a problem. But I know I will obviously need the copy constructor for when I implement the rest of the program. When I leave the copy constructor in, I can declare one set, either single or empty, and output its value. But if I declare a 2nd set, and i try to output either of the first two sets, i get a Segmentation Fault. Moreover, if i try to declare more then 2 sets, I get a Segmentation Fault. Any help would be appreciated!!</p> <p>Here is my code for a very basic implementation of everything:</p> <p><strong>Here is the setcalc.cpp: (main file)</strong></p> <pre><code>#include &lt;iostream&gt; #include &lt;cctype&gt; #include &lt;cstring&gt; #include &lt;string&gt; #include "strset2.h" using namespace std; // Declares of structure to hold all the sets defined struct setsOfStr { string nameOfSet; strSet stringSet; }; // Checks if the set name inputted is unique bool isSetNameUnique( vector&lt;setsOfStr&gt; strSetArr, string setName) { for(unsigned int i = 0; i &lt; strSetArr.size(); i++) { if( strSetArr[i].nameOfSet == setName ) { return false; } } return true; } int main() { char commandChoice; // Declares a vector with our declared structure as the type vector&lt;setsOfStr&gt; strSetVec; string setName; string singleEle; // Sets a loop that will constantly ask for a command until 'q' is typed while (1) { cin &gt;&gt; commandChoice; // declaring a set to be empty if(commandChoice == 'd') { cin &gt;&gt; setName; // Check that the set name inputted is unique if (isSetNameUnique(strSetVec, setName) == true) { strSet emptyStrSet; setsOfStr set1; set1.nameOfSet = setName; set1.stringSet = emptyStrSet; strSetVec.push_back(set1); } else { cerr &lt;&lt; "ERROR: Re-declaration of set '" &lt;&lt; setName &lt;&lt; "'\n"; } } // declaring a set to be a singleton else if(commandChoice == 's') { cin &gt;&gt; setName; cin &gt;&gt; singleEle; // Check that the set name inputted is unique if (isSetNameUnique(strSetVec, setName) == true) { strSet singleStrSet(singleEle); setsOfStr set2; set2.nameOfSet = setName; set2.stringSet = singleStrSet; strSetVec.push_back(set2); } else { cerr &lt;&lt; "ERROR: Re-declaration of set '" &lt;&lt; setName &lt;&lt; "'\n"; } } // using the output function else if(commandChoice == 'o') { cin &gt;&gt; setName; if(isSetNameUnique(strSetVec, setName) == false) { // loop through until the set name is matched and call output on its strSet for(unsigned int k = 0; k &lt; strSetVec.size(); k++) { if( strSetVec[k].nameOfSet == setName ) { (strSetVec[k].stringSet).output(); } } } else { cerr &lt;&lt; "ERROR: No such set '" &lt;&lt; setName &lt;&lt; "'\n"; } } // quitting else if(commandChoice == 'q') { break; } else { cerr &lt;&lt; "ERROR: Ignoring bad command: '" &lt;&lt; commandChoice &lt;&lt; "'\n"; } } return 0; } </code></pre> <p><strong>Here is the strSet2.h:</strong></p> <pre><code>#ifndef _STRSET_ #define _STRSET_ #include &lt;iostream&gt; #include &lt;vector&gt; #include &lt;string&gt; struct node { std::string s1; node * next; }; class strSet { private: node * first; public: strSet (); // Create empty set strSet (std::string s); // Create singleton set strSet (const strSet &amp;copy); // Copy constructor // will implement destructor and overloaded assignment operator later void output() const; }; // End of strSet class #endif // _STRSET_ </code></pre> <p><strong>And here is the strSet2.cpp (implementation of class)</strong></p> <pre><code>#include &lt;iostream&gt; #include &lt;vector&gt; #include &lt;string&gt; #include "strset2.h" using namespace std; strSet::strSet() { first = NULL; } strSet::strSet(string s) { node *temp; temp = new node; temp-&gt;s1 = s; temp-&gt;next = NULL; first = temp; } strSet::strSet(const strSet&amp; copy) { cout &lt;&lt; "copy-cst\n"; node *n = copy.first; node *prev = NULL; while (n) { node *newNode = new node; newNode-&gt;s1 = n-&gt;s1; newNode-&gt;next = NULL; if (prev) { prev-&gt;next = newNode; } else { first = newNode; } prev = newNode; n = n-&gt;next; } } void strSet::output() const { if(first == NULL) { cout &lt;&lt; "Empty set\n"; } else { node *temp; temp = first; while(1) { cout &lt;&lt; temp-&gt;s1 &lt;&lt; endl; if(temp-&gt;next == NULL) break; temp = temp-&gt;next; } } } </code></pre>
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