update

poj/1077.eight/main.cc

@@ -1,6 +1,13 @@
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
+#include <queue>
+#include <set>
+
+using std::priority_queue;
+using std::set;
+
+#define ABS(x) ((x) < 0 ? -(x) : (x))
 
 const int dst = 123456780;
 const int S = 362880;
@@ -70,39 +77,49 @@ int next_state(int p, char m) {
 }
 
 struct Node {
-  int sta;
-  int pre;
-  char mov;
-  Node(int sta = 0, int pre = 0, char mov = 0) : sta(sta), pre(pre), mov(mov) {}
+  int s;
+  int p;
+  int f;
+  int g;
+  int h;
+  char m;
+  Node(int s = 0, int p = 0, int f = 0, int g = 0, int h = 0, char m = 0)
+      : s(s), p(p), f(f), g(g), h(h), m(m) {}
+  bool operator<(const Node &that) const { return that.f < this->f; }
 } queue[S];
 
-int head, tail;
-
-bool used[S];
+int head;
 
 char moves[] = "udlr";
 char res[S + 1];
 
-bool bfs(int s, int t) {
-  head = 0, tail = 1;
+int eval_g(int s) {
+  int res = 0;
+  for (int i = 8; 0 <= i; i--) {
+    int c = s % 10;
+    if (c != 0) {
+      int x = (c - 1) / 3;
+      int y = (c - 1) % 3;
+      int cx = i / 3;
+      int cy = i % 3;
+      res += ABS(cx - x) + ABS(cy - y);
+    }
+    s /= 10;
+  }
+  return res;
+}
+
+bool a_star(int s, int t) {
+  head = 0;
   queue[head] = Node(s, -1);
-  memset(used, 0, sizeof(used));
-  used[perm2no(s)] = true;
-  while (head != tail) {
+  priority_queue<Node> pq;
+  pq.push(queue[head]);
+  set<int> used;
+  used.insert(s);
+  while (pq.size()) {
     Node &cur = queue[head];
-    if (cur.sta == t) return true;
-    for (int i = 0; i < 4; i++) {
-      char m = moves[i];
-      int nxt = next_state(cur.sta, m);
-      if (nxt == -1) continue;
-      int no = perm2no(nxt);
-      if (used[no]) continue;
-      queue[tail++] = Node(nxt, head, m);
-      used[no] = true;
-    }
     head++;
   }
-  return false;
 }
 
 int main() {
@@ -112,11 +129,11 @@ int main() {
     if (perm[i] == 'x') perm[i] = '0';
   }
   int src = atoi(perm);
-  if (bfs(src, dst)) {
+  if (a_star(src, dst)) {
     int pos = head, i = 0;
     do {
-      res[i++] = queue[pos].mov;
-      pos = queue[pos].pre;
+      res[i++] = queue[pos].m;
+      pos = queue[pos].p;
     } while (pos != -1);
     for (int j = i - 1; 0 <= j; j--) printf("%c", res[j]);
     printf("\n");