Posts by killerqb

I seem to have an error updating a checkbox using an SQL Query.
I am trying to get the box to be checked if equal to 1 and unchecked if equal to 0.

My database is updating correctly, but the checkbox is not.

<input type="checkbox" <?php if ($row['create_event'] = 1){ echo "checked='yes' value='check'";} else{ echo "checked='no' value='unchecked'";} ?> name="option1" > Create Event<br>

I call

echo $row['edit_event'];

before executing this line and it returns 0

I call

echo $row['edit_event'];

after executing this line and it returns 1

This makes me think that my if statement is really updating that row instead of performing a check. Any suggestions would be greatly appreciated.

This was actually the original function I found online, but I was trying to modify it in order to get it to work with my code. However I am unfamiliar with size_t and the U at the end of the InitialFNV initialization.
So can someone explain the U and size_t please.

static const size_t InitialFNV = 2166136261U;
static const size_t FNVMultiple = 16777619;

/* Fowler / Noll / Vo (FNV) Hash */
size_t myhash(const string &s)
{
    size_t hash = InitialFNV;
    for(size_t i = 0; i < s.length(); i++)
    {
        hash = hash ^ (s[i]);       /* xor  the low 8 bits */
        hash = hash * FNVMultiple;  /* multiply by the magic number */
    }
    return hash;
}

I was trying to play around with the FNV function but my program keeps seg faulting

static const unsigned InitialFNV = 2166136261;
static const unsigned FNVMultiple = 16777619;

// /* Fowler / Noll / Vo (FNV) Hash */
unsigned HashTable::hashFunc(const string &s)const
{
    unsigned hash = InitialFNV;
    for(unsigned i = 0; i < s.length(); i++)
    {
        hash = hash ^ (s[i]);       /* xor  the low 8 bits */
        hash = hash * FNVMultiple;  /* multiply by the magic number */
    }
    return hash;
}

Yes, sorry I meant speed by optimize, I guess I did not clarify. I'm kinda new to hash functions.

Thanks, but when I implemented your hash function it took nearly twice as long. Any other functions I should give a whirl?

I am trying to optimize my hash function, for a separate chaining hash table that I have created from scratch. My hash function is as follows:

int hash( const string &key, int tableSize)
        {
            int hashVal = 0;
			for(int i = 0; i<key.length();  i++)
			hashVal = 37*hashVal+key[i];
			hashVal %= tableSize;
			if(hashVal<0)
			hashVal += tableSize;
			return hashVal;
        }

I was wondering if one could point me to either a better hash function or how I should go about modifying this function.

Im sorry im not sure what your edit exactly means

My compiler is throwing me this error when I try to make a new one.
I am trying to make it with this

string a = "five";
   HashTable<string> *hashy =  new HashTable<string>(a,100);

This is the compiler error
(.text+0x1d3): undefined reference to `HashTable<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >::HashTable(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, int)'
collect2: ld returned 1 exit status

//
#include "hashTable.h"
#include <iostream>
#include <list>
#include <string>
#include <math.h>
#include <iterator>
bool checkforlargeprime (int num);
 
bool checkprime (int nn) {
    if (nn > 100) {
        return checkforlargeprime(nn);
    } else {
        int k=2;
        while (k < nn) {
            int sd = nn%k;
            if ( sd == 0) {
                return false;
            }
            k++;
        }
    }
    return true;
}
int getNextPrimeNumber (int num) {
    int nam = num+1;
    bool das = true;
    while ( das == true ) {
        if (checkprime(nam))
            das = false;
        else
            nam = nam+1;
    }
    return nam;
}
bool checkforlargeprime (int num) {
    if (num > 100) {
        int sss = ((int)(sqrt((double)num)))+1;
        int pn = 2;
 
        while (pn < sss) {
            if (num%pn == 0) {
                return false;
            }
            pn = getNextPrimeNumber(pn);
        }
        return true;
    } else {
        return false;
    }
}
 
template <class HashedObj>
        HashTable<HashedObj>::HashTable( const HashedObj & notFound, int size )
          : item( notFound ), theLists( getNextPrimeNumber( size ) )
        {
        }
template <class HashedObj>
        void HashTable<HashedObj>::insert( const HashedObj & x )
        {
            list<HashedObj> &whichList = theLists[hash(x, theLists.size())];
            typename std::list<HashedObj>::iterator itr = whichList.find(x);
 
            if( itr.isPastEnd( ) )
                whichList.insert( x, whichList.zeroth( ) );
        } …

Thanks, did that now, but now it gives me a compiler error of
undefined reference to `HashTable<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >::HashTable(std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, int)'
collect2: ld returned 1 exit status

When I declare a new Hashtable such as:
String a = null;
HashTable<string> = new HashTable(a, 100);

It tells me HashTable is not a type.

#ifndef HASHTABLE_H
        #define HASHTABLE_H
#include <iostream>
#include <vector>
#include <list>
using namespace std;
template <typename HashedObj>
 class HashTable
 {
 public:
 explicit HashTable( const HashedObj & notFound, int size = 101 );
 HashTable( const HashTable & rhs ): item( rhs.item ), theLists( rhs.theLists ) { }
 void makeEmpty();
 void insert(const HashedObj &x);
 void remove(const HashedObj &x);
 bool contains(const HashedObj &x)const;
 const HashedObj & find( const HashedObj & x ) const;
private:
const HashedObj item;
int size;
vector<list<HashedObj> > theLists;
};
template <typename HashedObj>
int hash(const HashedObj &x, int tablesize);
#endif

//
#include "hashTable.h"
#include <iostream>
#include <list>
#include <string>
#include <math.h>
#include <iterator>
bool checkforlargeprime (int num);

bool checkprime (int nn) {
    if (nn > 100) {
        return checkforlargeprime(nn);
    } else {
        int k=2;
        while (k < nn) {
            int sd = nn%k;
            if ( sd == 0) {
                return false;
            }
            k++;
        }
    }
    return true;
}
int getNextPrimeNumber (int num) {
    int nam = num+1;
    bool das = true;
    while ( das == true ) {
        if (checkprime(nam))
            das = false;
        else
            nam = nam+1;
    }
    return nam;
}
bool checkforlargeprime (int num) {
    if (num > 100) {
        int sss = ((int)(sqrt((double)num)))+1;
        int pn = 2;

        while (pn < sss) {
            if (num%pn == 0) {
                return false;
            }
            pn = getNextPrimeNumber(pn);
        }
        return true;
    } else { …

I know an AVL Tree guarantees a time of log(n), but what is the time cost of the actual re balancing of the tree and why is this ignored?

Well im not declaring it with new in the header file, so I guess, but I'm not exactly sure. I thought maybe because it was in the header it would be different.

My code is an expression tree program, in which I make treenodes pointers and push them in the end all into the 1st spot of a stack, in which is declared in my header file of the program. I wipe all the treenode pointers with a recursive traversal. Is this enough to prevent a memory leak or can the stack be deleted as well?

I'm creating an expression tree that reads in postfix notation and converts it and prints it out into infix notation. I was wondering how would I go about correctly distributing parentheses and balancing them properly.

I'm having a problem reading in a file to a scanner, it is supposed to take in a filename and then evaluate whether it is a URL or filename, but it having trouble reading just a local file.

public boolean loadSongs(String filename) {
		
		Scanner load1 = null;
		if (filename.contains("http")) {

			try {
				URL theFile = new URL(filename);
				load1 = new Scanner(theFile.openStream());
				while (load1.hasNextLine()) {

					String tempName = load1.nextLine();
					while (tempName.length() == 0) {
						tempName = load1.nextLine();
					}
					if (tempName.contains(" //")) {
						int slash = tempName.indexOf(" //");
						tempName = tempName.substring(0, slash);
					}
					String tempArtist = load1.nextLine();
					while (tempArtist.length() == 0) {
						tempArtist = load1.nextLine();
					}
					if (tempArtist.contains(" //")) {
						int slash = tempArtist.indexOf(" //");
						tempArtist = tempArtist.substring(0, slash);
					}
					String time = load1.nextLine();
					while (time.length() == 0) {
						time = load1.nextLine();
					}
					if (time.contains("//")) {
						int slash = time.indexOf("//") - 1;
						time = time.substring(0, slash);
					}

					int colon = time.indexOf(":");
					String min = time.substring(0, colon);
					int intmin = Integer.parseInt(min);
					String sec = time.substring(colon + 1);
					int intsec = Integer.parseInt(sec);
					if (intsec >= 60) {
						int minute = intsec / 60;
						intmin = intmin + minute;
						intsec = intsec - (60 * minute);
					}
					String stringURL = load1.nextLine();

					Song song = new Song(tempName, tempArtist, intmin, intsec,
							stringURL);
					this.songList.add(song);

				}

			} catch (IOException e) {
				System.out.println("could not access URL");
				e.printStackTrace();
				return false;
			}
		} else {
			// File theFile = new File(filename);
			File theFile1 = new File(filename);
			
			try {
				
				Scanner load = new Scanner(theFile1);
				while (load.hasNextLine()) {

					String tempName = load.nextLine();
					while …

Nvm, got it wasn't compiling it with the stack.cpp, whoops, thank you so much

thanks, but now its throwing me undefined reference errors when I try to run it

Here's the header of the postfix

#ifndef POSTFIXCALCULATOR_H
#define POSTFIXCALCULATOR_H
#include <iostream>
#include <stack>
using namespace std;





class postfixCalculator {
	public:
  int  evaluate(string word);			
	
};
#endif

This code worked when using #include <stack>, but I'm trying to implement my own

#include <iostream>
#include "postfixCalculator.h"
#include "stack.h"
using namespace std;

stack<int> stacky;
string calc;
string a;
int x;
int y;
int i;

int postfixCalculator::evaluate(string word){
  calc = word;
  while(calc.length()!=0){
   i = calc.find(" ");
 if( i >0 ){
  a = calc.substr(0,i);
 calc = calc.substr(i+1); 

 if(a.length() > 1)
   stacky.push(atoi(a.c_str()));
 else{
 switch(a[0]){
      case '+':      
       x = stacky.top();
        stacky.pop();
        y = stacky.top();
        stacky.pop();
	// cout << x + y << endl;
        stacky.push(x + y);
        break;
      case '-': 

        x = stacky.top();
        stacky.pop();
        y = stacky.top();
        stacky.pop();
	// cout << y - x << endl;
        stacky.push(y - x);
        break;
      case '*':

        x = stacky.top();
        stacky.pop();
        y = stacky.top();
        stacky.pop();
	// cout << x*y << endl;
        stacky.push(x*y);
        break;
case '~':

        x = stacky.top();
        stacky.pop();
	// cout << stacky.top() << endl;
        stacky.push(x*-1);
        break;
      case '/':                                                                          

        x = stacky.top();
        stacky.pop();
        y = stacky.top();
        stacky.pop();
	// cout << y/x << endl;
        stacky.push(y/x);
        break;
      default:
        stacky.push(atoi(a.c_str()));        
        break;
 }
 }
  }
else{
 switch(calc[0]){
      case '+':      
       x = stacky.top();
        stacky.pop();
        y = stacky.top();
        stacky.pop();
	// cout << x + y << endl;
        stacky.push(x + y);
        break;
      case '-': 

        x = stacky.top();
        stacky.pop();
        y = stacky.top();
        stacky.pop();
	// cout << y - x << endl;
        stacky.push(y - x);
        break;
      case '*':

        x = stacky.top();
        stacky.pop();
        y = stacky.top();
        stacky.pop();
        //cout << x*y << …

The stack.cpp is compiling fine now thank you, but when I try to implement it in my post fix calculator program it doesn't work. It goes back to the header file, but then claims that stack is not a template and the use of stack is ambgious and first declared as 'template<class T> struct stack' here. Should I add my postfix implementation

I'm having a problem with creating my own stack class and implementing it in a postfix calculator program I made. I was trying to make the stack.h file, but it keeps telling me stack is not a template

#ifndef STACK_H
#define STACK_H
#include <iostream>
using namespace std;

template <typename T>
class ListNode
{
public:
  ListNode();	
private:
    T value;
    ListNode<T> *next;
friend class  stack<T>;
    	
};

template <class T>
class stack
{
public:
  stack( ); 
  ~stack( ); 
  void push(T const&);
void makeEmpty();
  bool isEmpty() const;
  void pop();
 T top();
  
 private:
  ListNode<T> *topOfStack;

};
#endif

and here is my implementation:

#include <iostream>
#include "stack.h"
using namespace std;


template<typename T>
ListNode<T>::ListNode(){
  next = NULL;
 value = NULL;
};


template<typename T>
stack<T>::stack(){
  topOfStack = NULL;
};
template<typename T>
stack<T>::~stack(){
  makeEmpty();
}
template<typename T>
T stack<T>::top(){
  return topOfStack->value;
}
template<typename T>
void stack<T>::pop(){
  ListNode<T> *newnode = new ListNode<T>();
  topOfStack = topOfStack->next;
  delete newnode;
}
template<typename T>
bool stack<T>::isEmpty()const{
  return topOfStack==NULL;
}
template<typename T>
void stack<T>::makeEmpty(){
  while(!isEmpty()){
    pop();
  }
}

template<typename T>
void stack<T>::push(T const& x){
  ListNode<T> *newnode = new ListNode<T>();
  newnode->value = x;
  newnode->next = topOfStack;
  topOfStack = newnode;
}

int main(){
  return 0;
}

This is my first time working with templates so im not sure if its right