0126.骑士的攻击astar.md添加Java版本

problems/kamacoder/0126.骑士的攻击astar.md

@@ -335,6 +335,86 @@ IDA * 算法 对这一空间增长问题进行了优化，关于 IDA * 算法，
 
 ### Java 
 
+```java
+import java.util.PriorityQueue;
+import java.util.Scanner;
+
+class Knight implements Comparable<Knight> {
+    int x, y;
+    int g, h, f;
+
+    public Knight(int x, int y, int g, int h, int f) {
+        this.x = x;
+        this.y = y;
+        this.g = g;
+        this.h = h;
+        this.f = f;
+    }
+
+    @Override
+    public int compareTo(Knight k) {
+        return Integer.compare(this.f, k.f);
+    }
+}
+
+public class Main {
+    static int[][] moves = new int[1001][1001];
+    static int[][] dir = { {-2, -1}, {-2, 1}, {-1, 2}, {1, 2}, {2, 1}, {2, -1}, {1, -2}, {-1, -2} };
+    static int b1, b2;
+
+    static int Heuristic(Knight k) {
+        return (k.x - b1) * (k.x - b1) + (k.y - b2) * (k.y - b2);
+    }
+
+    static void astar(Knight k) {
+        PriorityQueue<Knight> que = new PriorityQueue<>();
+        que.add(k);
+        while (!que.isEmpty()) {
+            Knight cur = que.poll();
+            if (cur.x == b1 && cur.y == b2) {
+                break;
+            }
+            for (int i = 0; i < 8; i++) {
+                int nextX = cur.x + dir[i][0];
+                int nextY = cur.y + dir[i][1];
+                if (nextX < 1 || nextX > 1000 || nextY < 1 || nextY > 1000) {
+                    continue;
+                }
+                if (moves[nextX][nextY] == 0) {
+                    moves[nextX][nextY] = moves[cur.x][cur.y] + 1;
+                    Knight next = new Knight(nextX, nextY, cur.g + 5, Heuristic(new Knight(nextX, nextY, 0, 0, 0)), 0);
+                    next.f = next.g + next.h;
+                    que.add(next);
+                }
+            }
+        }
+    }
+
+    public static void main(String[] args) {
+        Scanner scanner = new Scanner(System.in);
+        int n = scanner.nextInt();
+        while (n-- > 0) {
+            int a1 = scanner.nextInt();
+            int a2 = scanner.nextInt();
+            b1 = scanner.nextInt();
+            b2 = scanner.nextInt();
+            for (int i = 0; i < 1001; i++) {
+                for (int j = 0; j < 1001; j++) {
+                    moves[i][j] = 0;
+                }
+            }
+            Knight start = new Knight(a1, a2, 0, Heuristic(new Knight(a1, a2, 0, 0, 0)), 0);
+            start.f = start.g + start.h;
+            astar(start);
+            System.out.println(moves[b1][b2]);
+        }
+        scanner.close();
+    }
+}    
+```
+
+
+
 ### Python
 
 ```Python 
@@ -683,4 +763,3 @@ int main() {
 
 
 
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