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// See LICENSE for license details.
//**************************************************************************
// Towers of Hanoi benchmark
//--------------------------------------------------------------------------
//
// Towers of Hanoi is a classic puzzle problem. The game consists of
// three pegs and a set of discs. Each disc is a different size, and
// initially all of the discs are on the left most peg with the smallest
// disc on top and the largest disc on the bottom. The goal is to move all
// of the discs onto the right most peg. The catch is that you are only
// allowed to move one disc at a time and you can never place a larger
// disc on top of a smaller disc.
//
// This implementation starts with NUM_DISC discs and uses a recursive
// algorithm to sovel the puzzle.
#include "util.h"
// This is the number of discs in the puzzle.
#define NUM_DISCS 7
//--------------------------------------------------------------------------
// List data structure and functions
struct Node
{
int val;
struct Node* next;
};
struct List
{
int size;
struct Node* head;
};
struct List g_nodeFreeList;
struct Node g_nodePool[NUM_DISCS];
int list_getSize( struct List* list )
{
return list->size;
}
void list_init( struct List* list )
{
list->size = 0;
list->head = 0;
}
void list_push( struct List* list, int val )
{
struct Node* newNode;
// Pop the next free node off the free list
newNode = g_nodeFreeList.head;
g_nodeFreeList.head = g_nodeFreeList.head->next;
// Push the new node onto the given list
newNode->next = list->head;
list->head = newNode;
// Assign the value
list->head->val = val;
// Increment size
list->size++;
}
int list_pop( struct List* list )
{
struct Node* freedNode;
int val;
// Get the value from the->head of given list
val = list->head->val;
// Pop the head node off the given list
freedNode = list->head;
list->head = list->head->next;
// Push the freed node onto the free list
freedNode->next = g_nodeFreeList.head;
g_nodeFreeList.head = freedNode;
// Decrement size
list->size--;
return val;
}
void list_clear( struct List* list )
{
while ( list_getSize(list) > 0 )
list_pop(list);
}
//--------------------------------------------------------------------------
// Tower data structure and functions
struct Towers
{
int numDiscs;
int numMoves;
struct List pegA;
struct List pegB;
struct List pegC;
};
void towers_init( struct Towers* this, int n )
{
int i;
this->numDiscs = n;
this->numMoves = 0;
list_init( &(this->pegA) );
list_init( &(this->pegB) );
list_init( &(this->pegC) );
for ( i = 0; i < n; i++ )
list_push( &(this->pegA), n-i );
}
void towers_clear( struct Towers* this )
{
list_clear( &(this->pegA) );
list_clear( &(this->pegB) );
list_clear( &(this->pegC) );
towers_init( this, this->numDiscs );
}
void towers_solve_h( struct Towers* this, int n,
struct List* startPeg,
struct List* tempPeg,
struct List* destPeg )
{
int val;
if ( n == 1 ) {
val = list_pop(startPeg);
list_push(destPeg,val);
this->numMoves++;
}
else {
towers_solve_h( this, n-1, startPeg, destPeg, tempPeg );
towers_solve_h( this, 1, startPeg, tempPeg, destPeg );
towers_solve_h( this, n-1, tempPeg, startPeg, destPeg );
}
}
void towers_solve( struct Towers* this )
{
towers_solve_h( this, this->numDiscs, &(this->pegA), &(this->pegB), &(this->pegC) );
}
int towers_verify( struct Towers* this )
{
struct Node* ptr;
int numDiscs = 0;
if ( list_getSize(&this->pegA) != 0 ) {
return 2;
}
if ( list_getSize(&this->pegB) != 0 ) {
return 3;
}
if ( list_getSize(&this->pegC) != this->numDiscs ) {
return 4;
}
for ( ptr = this->pegC.head; ptr != 0; ptr = ptr->next ) {
numDiscs++;
if ( ptr->val != numDiscs ) {
return 5;
}
}
if ( this->numMoves != ((1 << this->numDiscs) - 1) ) {
return 6;
}
return 0;
}
//--------------------------------------------------------------------------
// Main
int main( int argc, char* argv[] )
{
struct Towers towers;
int i;
// Initialize free list
list_init( &g_nodeFreeList );
g_nodeFreeList.head = &(g_nodePool[0]);
g_nodeFreeList.size = NUM_DISCS;
g_nodePool[NUM_DISCS-1].next = 0;
g_nodePool[NUM_DISCS-1].val = 99;
for ( i = 0; i < (NUM_DISCS-1); i++ ) {
g_nodePool[i].next = &(g_nodePool[i+1]);
g_nodePool[i].val = i;
}
towers_init( &towers, NUM_DISCS );
// If needed we preallocate everything in the caches
#if PREALLOCATE
towers_solve( &towers );
#endif
// Solve it
towers_clear( &towers );
setStats(1);
towers_solve( &towers );
setStats(0);
// Check the results
return towers_verify( &towers );
}
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