[20250821] BOJ / G1 / 청소년 상어 / 이준희

JHLEE325/202508/21 BOJ G1 청소년 상어.md

@@ -0,0 +1,147 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    static int[] dr = {-1, -1, 0, 1, 1, 1, 0, -1};
+    static int[] dc = { 0, -1,-1,-1, 0, 1, 1,  1};
+
+    static class fish {
+        int r, c, dir;
+        boolean live;
+
+        public fish(int row, int col, int d) {
+            this.r = row;
+            this.c = col;
+            this.dir = d;
+            this.live = true;
+        }
+    }
+
+    static class shark {
+        int r, c, eat, dir;
+
+        public shark(int row, int col, int e, int d) {
+            this.r = row;
+            this.c = col;
+            this.eat = e;
+            this.dir = d;
+        }
+    }
+
+    static int[][] map = new int[4][4];
+    static fish[] list = new fish[17];
+    static int answer = 0;
+
+    public static void main(String[] args) throws Exception {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st;
+
+        shark s = null;
+
+        for (int i = 0; i < 4; i++) {
+            st = new StringTokenizer(br.readLine());
+            for (int j = 0; j < 4; j++) {
+                int n = Integer.parseInt(st.nextToken());
+                int d = Integer.parseInt(st.nextToken()) - 1;
+                map[i][j] = n;
+                list[n] = new fish(i, j, d);
+            }
+        }
+
+        int first = map[0][0];
+        fish f0 = list[first];
+        f0.live = false;
+        s = new shark(0, 0, first, f0.dir);
+        map[0][0] = 0;
+
+        dfs(copymap(map), copylist(list), s);
+
+        System.out.println(answer);
+    }
+
+    static void dfs(int[][] curmap, fish[] curlist, shark s) {
+        answer = Math.max(answer, s.eat);
+
+        moveFish(curmap, curlist, s);
+
+        int sr = s.r, sc = s.c, dir = s.dir;
+        for (int step = 1; step <= 3; step++) {
+            int nr = sr + dr[dir] * step;
+            int nc = sc + dc[dir] * step;
+
+            if (nr < 0 || nr >= 4 || nc < 0 || nc >= 4) break;
+            if (curmap[nr][nc] == 0) continue;
+
+            int[][] nMap = copymap(curmap);
+            fish[] nList = copylist(curlist);
+
+            int target = nMap[nr][nc];
+            fish eaten = nList[target];
+            eaten.live = false;
+
+            shark ns = new shark(nr, nc, s.eat + target, eaten.dir);
+
+            nMap[sr][sc] = 0;
+            nMap[nr][nc] = 0;
+
+            dfs(nMap, nList, ns);
+        }
+    }
+
+    static void moveFish(int[][] curmap, fish[] curlist, shark s) {
+        for (int i = 1; i <= 16; i++) {
+            fish f = curlist[i];
+            if (f == null || !f.live) continue;
+
+            for (int rotate = 0; rotate < 8; rotate++) {
+                int nd = (f.dir + rotate) % 8;
+                int nr = f.r + dr[nd];
+                int nc = f.c + dc[nd];
+
+                if (nr < 0 || nr >= 4 || nc < 0 || nc >= 4) continue;
+                if (nr == s.r && nc == s.c) continue;
+
+                if (curmap[nr][nc] == 0) {
+                    curmap[f.r][f.c] = 0;
+                    f.r = nr; f.c = nc; f.dir = nd;
+                    curmap[nr][nc] = i;
+                } else {
+                    int otherNum = curmap[nr][nc];
+                    fish g = curlist[otherNum];
+
+                    curmap[f.r][f.c] = otherNum;
+                    curmap[nr][nc] = i;
+
+                    int tr = f.r, tc = f.c;
+                    f.r = nr; f.c = nc; f.dir = nd;
+                    g.r = tr; g.c = tc;
+                }
+                break;
+            }
+        }
+    }
+
+    static int[][] copymap(int[][] src) {
+        int[][] cpymap = new int[4][4];
+        for (int i = 0; i < 4; i++) {
+            System.arraycopy(src[i], 0, cpymap[i], 0, 4);
+        }
+        return cpymap;
+    }
+
+    static fish[] copylist(fish[] src) {
+        fish[] cpylist = new fish[17];
+        for (int i = 1; i <= 16; i++) {
+            if (src[i] == null) continue;
+            fish f = src[i];
+            fish nf = new fish(f.r, f.c, f.dir);
+            nf.live = f.live;
+            cpylist[i] = nf;
+        }
+        return cpylist;
+    }
+}
+
+```