UVa10085 - The most distant state

#include <stdio.h>
#include <string.h>

#define N 3
#define MAX 3000000
#define HASHSIZE 1000003
#define DIRSIZE 100
typedef struct node
{
int x, y, step;
int a

;
char dir[DIRSIZE];
}node;

node queue[MAX];
int startx, starty;
int dx[] = {0, 0, -1, 1};
int dy[] = {1, -1, 0, 0};
int head[HASHSIZE], next[MAX];
char dir[] = "RLUD";

int bfs();
void init_loopup_table();
int try_to_insert(int s);
int hash(node s);
void print(node s);

int main()
{
int iCase;
int i, j, cas;
int ans;

#ifndef ONLINE_JUDGE
freopen("d:\\UVa\\uva_in.txt", "r", stdin);
#endif

scanf("%d", &iCase);

for (cas = 0; cas < iCase; cas++) {
for (i = 0; i < N; i++) {
for (j = 0; j < N; j++) {
scanf("%d", &queue[0].a[i][j]);
if (queue[0].a[i][j] == 0)
startx = i, starty = j;
}
}

ans = bfs() - 1;

printf("Puzzle #%d\n", cas + 1);

for (i = 0; i < N; i++) {
for (j = 0; j < N; j++) {
if (j)
printf(" ");
printf("%d", queue[ans].a[i][j]);
}
printf("\n");
}
queue[ans].dir[queue[ans].step] = '\0';
printf("%s\n", queue[ans].dir);
printf("\n");
}

return 0;
}

int bfs()
{
int front = 0, rear = 1;
node tmp, newstate;
int i;
int newx, newy, tmpx, tmpy;

queue[0].x = startx, queue[0].y = starty, queue[0].step = 0;
init_loopup_table();

while (front < rear) {
tmp = queue[front];
for (i = 0; i < 4; i++) {
tmpx = tmp.x;
tmpy = tmp.y;
newx = tmpx + dx[i];
newy = tmpy + dy[i];

if (newx >= 0 && newx < 3 && newy >= 0 && newy < 3) {
newstate = tmp;
newstate.a[newx][newy] = tmp.a[tmpx][tmpy];
newstate.a[tmpx][tmpy] = tmp.a[newx][newy];
newstate.x = newx;
newstate.y = newy;
newstate.step++;
newstate.dir[newstate.step - 1] = dir[i];
queue[rear] = newstate;

if (try_to_insert(rear)) {
rear++;
}
}
}

front++;
}

return rear;
}

void init_loopup_table()
{
memset(head, -1, sizeof(head));
memset(next, -1, sizeof(next));
try_to_insert(0);
}

int hash(node s)
{
int i, j;
int res = 0;

for (i = 0; i < 3; i++) {
for (j = 0; j < 3; j++) {
res = res * 10 + s.a[i][j];
}
}

return res % HASHSIZE;
}

int try_to_insert(int s)
{
int h = hash(queue[s]);
int u = head[h];

while (u != -1) {
if (memcmp(queue[u].a, queue[s].a, sizeof(queue[s].a)) == 0)
return 0;
u = next[u];
}

next[s] = head[h];
head[h] = s;

return 1;
}

void print(node s)
{
int i, j;

for (i = 0; i < N; i++) {
for (j = 0; j < N; j++) {
printf("%d ", s.a[i][j]);
}
printf("\n");
}
printf("\n");
}