Agfdhyk

I am implementing a hashtable and am having trouble with the implementation. After literal hours of googling on this one thing, i've given up and was hoping to see of i could get any help here. The biggest issue is to do with the use of vectors in the HashTable(doesnt make sense to me, rather just use list<> but using it is required)

My main issue is to do with how to implement the insert function to add to the HashTable.

void HashTable::insert(ulint key,ulint value){  //insert data associated with key



   HashNode nodeToAdd;

   nodeToAdd.assign(key, value);



   int index = hash_function(key);



   this->table[index].push_back(nodeToAdd);



   }

Now the issue im having is adding the HashNode to my HashTable.

for reference in HashTable, the field for the table is

typedef vector <list<HashNode> > Table;

Table *table;

So by my understanding

   this->table[index].push_back(nodeToAdd);

is going to the vector HashTable[index], which at the index should be a list. and when it gets to that list, it should push_back the new node into the list.

However when compiled, i'm hit by an error(no matching function to call) and i don't understand why.

Your list stores objects of type HashNode, not type HashNode*.

So you need to decide which of those you want to use, and change the code accordingly.

1. If you want to keep storing HashNode, then your insert is wrong -- it should instead create the node on the stack and store it by value in the list.




2. If you want to store a pointer, then your Table type is wrong, and should instead be vector<list<HashNode*>> -- note it should be managed carefully since the pointers will not be automatically deleted.

Personally, I'd suggest you go with #1 and save yourself a whole lot of headaches. But if you insist on #2, then I suggest you stop using malloc and use new -- or better yet use std::unique_ptr or std::shared_ptr for automatic lifetime management.

Also noteworthy is your definition Table *table. This is baffling, since Table is a vector. Your insert function is dereferencing this pointer, expecting it to perhaps point to an array of Table values, when it's quite clear you actually think it's a vector. I'm pretty sure you don't want that to be a pointer.

Since I only just noticed that detail, I imagine that's the first source of your error, since table[index] is actually type Table, not type list<HashNode> and you were trying to call the non-existent function vector<list<HashNode>>::push_back(HashNode*).