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knapsack.c
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knapsack.c
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#include "knapsack.h"
void print_grid(cell **grid, item *store, int c, int r)
{
int i;
int j;
printf("\n ");
i = -1;
while (++i <= c)
printf(" %2i ", i);
printf("\n---------");
i = -1;
while (++i <= c)
printf("----------");
printf("\n");
j = -1;
while (++j <= r)
{
printf("%.5s ", store[j].name);
printf("%i | ", j);
i = -1;
while (++i <= c)
{
printf("%2i %2i ", grid[j][i].load, grid[j][i].sum);
if (!grid[j][i].sack)
printf("0 | ");
else
printf("+ | ");
}
printf("\n");
}
printf("---------");
i = -1;
while (++i <= c)
printf("----------");
printf("\n");
}
loot *new_loot(item *stuff)
{
loot *new;
if (stuff)
{
if (!(new = malloc(sizeof(*new))))
return (NULL);
new->stolen = stuff;
new->next = NULL;
return (new);
}
return (NULL);
}
void put_in_sack(cell *dest, item *stuff, cell *src)
{
loot *add_here;
add_here = NULL;
if (stuff)
{
dest->load += stuff->wt;
dest->sum += stuff->val;
dest->sack = new_loot(stuff);
add_here = dest->sack;
}
dest->load += src->load;
dest->sum += src->sum;
if (!add_here)
dest->sack = src->sack;
else
add_here->next = src->sack;
}
int steal(item *store, cell **grid, int capacity, int item_count)
{
/* row and column */
int r;
int c;
r = 0;
/* iterate on items */
while (++r <= item_count)
{
c = 0;
/* iterate on subknapsacks */
while (++c <= capacity)
{
/* will current item fit? */
if (store[r].wt <= c)
{
/* Is it worth taking?
* Combine current item's value with the total value of loot for the remaining space.
* If (1) value is greater than previous solution for this capacity or
* (2) values are equal, but taking new item leaves more free space */
if ((store[r].val + grid[r - 1][c - store[r].wt].sum > grid[r - 1][c].sum)
|| ((store[r].val + grid[r - 1][c - store[r].wt].sum == grid[r - 1][c].sum)
&& (grid[r - 1][c - store[r].wt].load + store[r].wt < grid[r - 1][c].load)))
{
put_in_sack(&grid[r][c], &store[r], &grid[r - 1][c - store[r].wt]);
}
else
/* else copy from previous row */
put_in_sack(&grid[r][c], NULL, &grid[r - 1][c]);
}
/* if it doesn't fit, also copy from previous row */
else
put_in_sack(&grid[r][c], NULL, &grid[r - 1][c]);
}
}
return (1);
}
int fill_store(item **store, char **s, int cnt)
{
int i;
int j;
if (!(*store = malloc(sizeof(item) * cnt)))
return (0);
(*store)[0].name = " ";
(*store)[0].wt = 0;
(*store)[0].val = 0;
i = 0;
j = 0;
while (++j < cnt)
{
(*store)[j].name = s[i];
(*store)[j].wt = atoi(s[i + 1]);
(*store)[j].val = atoi(s[i + 2]);
i += 3;
}
return (1);
}
cell **create_grid(cell **grid, int c, int r)
{
int i;
int j;
if (!(grid = malloc(sizeof(*grid) * r)))
return (NULL);
j = -1;
while (++j < r)
{
if (!(grid[j] = malloc(sizeof(cell) * c)))
return (NULL);
i = -1;
while (++i < c)
{
grid[j][i].load = 0;
grid[j][i].sum = 0;
grid[j][i].sack = NULL;
}
}
return (grid);
}
void free_grid(cell **grid, int c, int r)
{
int x;
int y;
loot *tmp;
loot *prev;
/* first go: mark and detach */
/*iterate on rows and columns */
y = -1;
while (++y <= r)
{
x = -1;
while (++x <= c)
{
tmp = grid[y][x].sack;
/* if sack is pointing to a marked data, detach it */
if (tmp && !tmp->stolen)
grid[y][x].sack = NULL;
else
{
/* traverse the list and mark all data; if encountered marked data in next - detach */
while (tmp)
{
tmp->stolen = NULL;
if (tmp->next && !tmp->next->stolen)
tmp->next = NULL;
tmp = tmp->next;
}
}
}
}
/* second go: free */
y = -1;
while (++y <= r)
{
x = -1;
while (++x <= c)
{
tmp = grid[y][x].sack;
while (tmp)
{
prev = tmp;
tmp = tmp->next;
free(prev);
}
}
free(grid[y]);
}
free(grid);
}
int main(int argc, char **argv)
{
int capacity;
int item_count;
item *store;
cell **grid;
loot *tmp;
int i;
if ((argc - 2) % 3)
printf("usage: ./bin <knapsack_capacity> <item_1_name> <item_1_weight> <item_1_value> ... <item_n_name> <item_n_weight> <item_n_value>\n");
else
{
capacity = atoi(argv[1]);
item_count = (argc - 2) / 3;
/* first item is a dummy to simplify syntax */
if (!(fill_store(&store, argv + 2, item_count + 1)))
return (10);
/* print vars and store */
printf("capacity %i, item count %i\n", capacity, item_count);
i = 0;
while (++i <= item_count)
printf("%s w%i v%i, ", (store + i)->name, (store + i)->wt, (store + i)->val);
printf("\n");
/* capacity = 0 and item = 0 will be zeroed grid margins */
grid = NULL;
if (!(grid = create_grid(grid, capacity + 1, item_count + 1)))
return (10);
print_grid(grid, store, capacity, item_count);
steal(store, grid, capacity, item_count);
print_grid(grid, store, capacity, item_count);
printf("total loot value: %i, total loot weight: %i (of %i capacity)\nstolen items: ", grid[item_count][capacity].sum, grid[item_count][capacity].load, capacity);
tmp = grid[item_count][capacity].sack;
while (tmp)
{
printf("%s ", tmp->stolen->name);
tmp = tmp->next;
}
printf("\n");
free_grid(grid, capacity, item_count);
free(store);
}
}