C++ Bin Packing Implementation using First Fit - c++

Question

I'm doing a project for university but I encountered an exception which I don't understand. I'm using S.Sahni algorithms, so mostly I've got the code from his book. What I'm trying to do is to implement the Bin Packing problem with First Fit while I'm using tournament trees (max winner).
Here is my header:
// file winner.h
#ifndef WinnerTree_
#define WinnerTree_
#include <iostream>
#include <stdlib.h>
#include "xcept.h"
using namespace std;
template<class T>
class WinnerTree {
public:
WinnerTree(int TreeSize = 10);
~WinnerTree() {delete [] t;}
void Initialize(T a[], int size, int (&winner)(T a[], int player1, int player2));
int Winner()
{return (n) ? t[1] : 0;}
int Winner(int i)
{return (i < n) ? t[i] : 0;}
void RePlay(int i, int (&winner)(T a[], int player1, int player2));
void Output();
private:
int MaxSize;
int n; // current size
int LowExt; // lowest-level external nodes
int offset; // 2^k - 1
int *t; // array for winner tree
T *e; // element array
void Play(int p, int lc, int rc, int (&winner)(T a[], int player1, int player2));
};
template<class T>
WinnerTree<T>::WinnerTree(int TreeSize)
{// Constructor for winner tree.
MaxSize = TreeSize;
t = new int[MaxSize];
n = 0;
}
template<class T>
void WinnerTree<T>::Initialize(T a[], int size, int (&winner)(T a[], int player1, int player2))
{// Initialize winner t for array a.
if (size > MaxSize || size < 2)
throw BadInput();
n = size;
e = a;
// compute s = 2^log (n-1)
int i, s;
for (s = 1; 2*s <= n-1; s += s);
LowExt = 2*(n-s);
offset = 2*s-1;
// play matches for lowest-level external nodes
for (i = 2; i <= LowExt; i += 2)
Play((offset+i)/2, i-1, i, winner);
// handle remaining external nodes
if (n % 2) {// special case for odd n, play
// internal and external node
Play(n/2, t[n-1], LowExt+1, winner);
i = LowExt+3;}
else
i = LowExt+2;
// i is left-most remaining external node
for (; i <= n; i += 2)
Play((i-LowExt+n-1)/2, i-1, i, winner);
}
template<class T>
void WinnerTree<T>::Play(int p, int lc, int rc, int (&winner)(T a[], int player1, int player2))
{// Play matches beginning at t[p].
// lc and rc are the children of t[p].
t[p] = winner(e, lc, rc);
// more matches possible if at right child
while (p > 1 && p % 2) {// at a right child
t[p/2] = winner(e, t[p-1], t[p]);
p /= 2; // go to parent
}
}
template<class T>
void WinnerTree<T>::RePlay(int i, int(&winner)(T a[], int player1, int player2))
{// Replay matches for element i.
if (i <= 0 || i > n)
throw OutOfBounds();
int p, // match node
lc, // left child of p
rc; // right child of p
// find first match node and its children
if (i <= LowExt) {// begin at lowest level
p = (offset + i)/2;
lc = 2*p - offset; // left child of p
rc = lc+1;}
else {
p = (i-LowExt+n-1)/2;
if (2*p == n-1) {
lc = t[2*p];
rc = i;}
else {
lc = 2*p - n + 1 + LowExt;
rc = lc+1;}
}
t[p] = winner(e, lc, rc);
// play remaining matches
p /= 2; // move to parent
for (; p >= 1; p /= 2)
t[p] = winner(e, t[2*p], t[2*p+1]);
}
template<class T>
void WinnerTree<T>::Output()
{
cout << "size = "<< n << " LowExt = " << LowExt
<< " Offset = " << offset << endl;
cout << "Winner tree pointers are" << endl;
for (int i = 1; i < n; i++)
cout << t[i] << ' ';
cout << endl;
}
#endif
This is my exception file:
#ifndef Xcept_
#define Xcept_
#include <exception>
#include <new.h>
// bad initializers
class BadInitializers {
public:
BadInitializers() {}
};
// insufficient memory
class NoMem {
public:
NoMem() {}
};
// change new to throw NoMem instead of xalloc
void my_new_handler()
{
throw NoMem();
};
new_handler Old_Handler_ = set_new_handler(my_new_handler);
// improper array, find, insert, or delete index
// or deletion from empty structure
class OutOfBounds {
public:
OutOfBounds() {}
};
// use when operands should have matching size
class SizeMismatch {
public:
SizeMismatch() {}
};
// use when zero was expected
class MustBeZero {
public:
MustBeZero() {}
};
// use when zero was expected
class BadInput {
public:
BadInput() {}
};
#endif
And this is my main function:
// First fit bin packing
#include "stdafx.h"
using namespace std;
#include <iostream>
#include "winner.h"
int winner(int a[], int player1, int player2)
{// For a max winner tree.
if (a[player1] >= a[player2])
return player1;
return player2;
}
void FirstFitPack(int s[], int n, int c)
{// Output first fit packing into bins of size c.
// n is the number of objects and s[] their size.
WinnerTree<int> *W = new WinnerTree<int>(n);
int *avail = new int[n + 1]; // bins
// initialize n bins and winner tree
for (int i = 1; i <= n; i++)
avail[i] = c; // initial available capacity
W->Initialize(avail, n, winner);
// put objects in bins
for (int i = 1; i <= n; i++) {// put s[i] in a bin
// find first bin with enough capacity
int p = 2; // start search at left child of root
while (p < n) {
int winp = W->Winner(p);
if (avail[winp] < s[i]) // first bin is in
p++; // right subtree
p *= 2; // move to left child
}
int b; // will be set to bin to use
p /= 2; // undo last left child move
if (p < n) {// at a tree node
b = W->Winner(p);
// if b is right child, need to check
// bin b-1. No harm done by checking
// bin b-1 even if b is left child.
if (b > 1 && avail[b - 1] >= s[i])
b--;
}
else // arises when n is odd
b = W->Winner(p / 2);
cout << "Pack object " << i << " in bin "
<< b << endl;
avail[b] -= s[i]; // update avail. capacity
W->RePlay(b, winner);
getchar();
}
}
int main(void)
{
int n, c; // number of objects and bin capacity
cout << "Enter number of objects" << endl;
cin >> n;
if (n < 2) {
cout << "Too few objects" << endl;
exit(1);
}
cout << "Enter bin capacity" << endl;
cin >> c;
int *s = new int[n + 1];
for (int i = 1; i <= n; i++) {
cout << "Enter space requirement of object " << i << endl;
cin >> s[i];
if (s[i] > c) {
cout << "Object too large to fit in a bin" << endl;
exit(1);
}
}
FirstFitPack(s, n, c);
return 0;
}
The exception that I get is:
First-chance exception at 0x0012668D in Bin Packing-FF.exe: 0xC0000005: Access violation reading location 0xF9039464.
I know that I'm getting this exception because of the winner. But I can't understand what I have to change here.
int winner(int a[], int player1, int player2)
{// For a max winner tree.
if (a[player1] >= a[player2])
return player1;
return player2;
}
Also, If I press space or enter after the last input (object) then I don't get the exception and everything is going smoothly. But still I want to know why I'm getting this exception.
Thank you in advance.