C++ Hash Table and Linked List Issues - c++

Question

So I'm trying to work on a project for my C++ class where I read a .txt file that has 53 lines of cities, states, and superfluous information afterwards.
(example: Port Jervis,NY,New York,36071,Orange,36071,41.3782,-74.6909,16410.0,1317)
After reading the file, I separate out the city name (example: Port Jervis) and state code (example: NY) and uses the value of the two letters in the state code as the key for a hash table of 13 elements. So N=13 + Y=24 = key of 37, and since the hash has 13 elements it's 37 % 13 = hash-key of 11.
So far so good and I'm able to get all that done correctly, however when it comes to displaying the results is where I'm running into an issue as each element of the hash-table is missing one link in the linked list. So it only displays 40 outputs of the 53, with 1 missing per element and I'm really not sure why.
So I e-mailed my professor my code and he said that my insert method is not correct which he believes is causing this error. My current insert method looks like
void insert(int key, string city, string state)//insert value
{
int hash = KeyModFunction(key); //function that's %13 for hash-key
Node* tmpInsert = new Node(key, city, state); //create node to work with
if(table[hash]==NULL)//checks if table is empty
{
table[hash] = tmpInsert; //if empty, make new node with key/city/state values
}
else//if not empty
{
Node *runner = table[hash]; //made node to run through the list
while(runner->next != NULL)//make it to the end
{
runner=runner->next; // go go go
}
runner->next = tmpInsert; //and point the end at the new node to be inserted
}
} //end insert
And my professor suggested it should look something more like
if(table[hash]->next == NULL)
{
table[hash]->next = tmpInsert;
table[hash]->myCity = city;
table[hash]->myState = state;
}
else
{
// You can figure out the else code based on the above
However, whenever I put that into my code, it no longer compiles and says there is a segment fault. But when I run it through a debugger it says "[Inferior 1 (process 5453) exited normally]" which I'm not going to lie, I'm not sure what the means and have been unable to find a concrete answer online for. But I'm assuming the exited normally is a good thing, however, nothing is displayed.
I've been beating my head against this all week trying to figure out a solution and it's finally come to the point where I know I'm just getting too in my own head about it, so I've come here hoping to find some guidance, advice, or at the very least someone to point me in the right direction. If more of my code is needed on here, let me know, I just didn't want to dump my whole project on here cause I legitimately want to figure it out instead of having someone just do it for me, but yeah, I'm stuck. Thanks in advance for any help!
****2:12PST - 5/17/2020 UPDATE****
So in all fairness the insert code was plucked and modified from other peoples code I've found online looking into how to do this, so that might be why it looks better than my professor (also I'm pretty sure he mention C++ isn't his most familiar language). And yes, we are supposed to implement the hash table ourselves.
So here is the full program:
class Node{
public:
int key;
string myCity;
string myState;
Node *next;
Node(int key, string myCity, string myState)//constructor
{
this->key = key;
this->myCity = myCity;
this->myState = myState;
this->next = NULL;
}
};//end Node
class Hash{
private:
int BUCKET; //number of over all values
Node** table;
public:
//Constructor
Hash(int V)
{
this->BUCKET = V; //setting the BUCKET size to max number of enteries
table = new Node*[BUCKET]; //create table with size of BUCKET
for(int i = 0; i < BUCKET; i++) //fill table with NULL values
{
table[i] = NULL;
}
} //end constructor
//KeyModFunction
int KeyModFunction(int x) //getting the hash key value
{
return (x % BUCKET);
} //end KeyModFunction
//Insert Function
void insert(int key, string city, string state)//insert value
{
int hash = KeyModFunction(key); //function that's %13 for hash-key
Node* tmpInsert = new Node(key, city, state); //create node to work with
if(table[hash]==NULL)//checks if table is empty
{
table[hash] = tmpInsert; //if empty, make new node with key/city/state values
}
else//if not empty
{
Node *runner = table[hash]; //made node to run through the list
while(runner->next != NULL)//make it to the end
{
runner=runner->next; // go go go
}
runner->next = tmpInsert; //and point the end at the new node to be inserted
}
} //end insert
//Display function
void displayHash()
{
for(int loop = 0; loop < BUCKET; loop++)
{
cout<<loop;
if(table[loop]->next != NULL)
{
Node* tmp;
tmp = table[loop]->next;
do
{
cout<<" -->"<<tmp->myCity<<"/"<<tmp->myState;
tmp = tmp->next;
}while(tmp!=NULL);
}
cout<<endl;
}
}//end displayHash
}; //end Hash Class
int main() {
cout << "CSP 31B - Read and Process Assignment\n\n";
char myAlpha[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"; //the key array for all the letter values
Hash myTbl(13); //create hashmap with BUCKET size of 13
string fCity, fState, fExtra; //string variables to hold info
int key = 0; //hash value of the state code (two letters added together)
ifstream myfile("CityOut.txt");
while ( getline(myfile, fCity, ',') && getline(myfile, fState, ','))
{
getline(myfile, fExtra);
for(int i = 0; i < sizeof(myAlpha)/sizeof(myAlpha[0]); i++)
{
if(fState.at(0) == myAlpha[i])
{
key += i;
}
else if(fState.at(1) == myAlpha[i])
{
key += i;
}
}
int checkNum = 1;
cout << "DEBUGGER: City name: "<<fCity <<" State code: " << fState.at(0) << fState.at(1) <<" key = "<<key<<endl; //temporary statement for debugging purposes
myTbl.insert(key, fCity, fState);
key = 0; //reset hash number to zero for next line of CityOut.txt
}
cout<<endl<<endl<<endl;
myTbl.displayHash();
return 0;
}//end main
Then the output should look something like:
but each table element should have 1 more output

Answer 1

Your print code skips the first element of your hash table.
This code:
cout<<loop;
if(table[loop]->next != NULL)
{
Node* tmp;
tmp = table[loop]->next;
do
{
cout<<" -->"<<tmp->myCity<<"/"<<tmp->myState;
tmp = tmp->next;
}while(tmp!=NULL);
}
Should be :
cout<<loop;
if(table[loop] != NULL)
{
Node* tmp;
tmp = table[loop];
do
{
cout<<" -->"<<tmp->myCity<<"/"<<tmp->myState;
tmp = tmp->next;
}while(tmp!=NULL);
}