graph using adjacency list

#include<iostream>

using namespace std;

class Graph{
public:
void addVertex(int vertex);
void display();
TCSGraph(){

head = NULL;
}
~Graph(){}

private:
struct ListNode
{
string name;
struct ListNode *next;
};

ListNode *head;
};

void Graph::addVertex(int vertex){
ListNode *newNode;
ListNode *nodePtr;
string vName;

for(int i = 0; i < vertex ; i++ ){
cout << "what is the name of the vertex"<< endl;
cin >> vName;
newNode = new ListNode;
newNode->name = vName;
newNode->next = NULL;

if (!head)
head = newNode;
else{
nodePtr = head;
while(nodePtr->next)
nodePtr = nodePtr->next;

nodePtr->next = newNode;

}
}
}

void Graph::display(){
ListNode *nodePtr;
nodePtr = head;

while(nodePtr){
cout << nodePtr->name<< endl;
nodePtr = nodePtr->next;
}
}

void displayMenu(){
cout << endl << endl;
cout << " 1. Add a vertice" << endl;
cout << " 2. Displaying a graph by printing out the adjacency lists" << endl;
cout << " 0. Quit" << endl;
cout << endl;
cout << "Please enter your option: ";
}

int main(){

int choice;
int vertex;
bool done = false;

do{
displayMenu();
cin >> choice;
TCSGraph g;

if(choice==1){
cout << " how many vertex u wan to add" << endl;
cin >> vertex;
g.addVertex(vertex);
}
else if (choice==2){
g.display();
}
}while(!done);

return 0;
}

Hello,
your problem is that every pass of the loop, you create and destroy the TCSGraph object. Therefore it is always empty when you try to display it.
You have to put the declaration of the variable before the loop.

Second, you don't dealocate the dynamically created Nodes when TCSGraph is destroyed, which results in memory leaks.

And last but not least, if this is the verbatim source, learn to indent the code properly. It helps with reading and orientation immensely.

Quote:

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Originally Posted by MirekCerny

Hello,
your problem is that every pass of the loop, you create and destroy the TCSGraph object. Therefore it is always empty when you try to display it.
You have to put the declaration of the variable before the loop.

Second, you don't dealocate the dynamically created Nodes when TCSGraph is destroyed, which results in memory leaks.

And last but not least, if this is the verbatim source, learn to indent the code properly. It helps with reading and orientation immensely.

---

The web site destroys indention unless you use [CODE and [/CODE tags.