[20250312] BOJ / G3 / 캐슬 디펜스 / 신동윤

03do-new30/202503/12 BOJ G3 캐슬 디펜스.md

@@ -0,0 +1,112 @@
+```java
+import java.io.*;
+import java.util.*;
+
+public class Main {
+
+    static int N, M, D, maxEnemy;
+    static int[][] original;
+    static int[] archerCols;
+
+    public static void main(String[] args) throws IOException {
+        input();
+        archerCols = new int[3];
+        maxEnemy = 0;
+        combination(0, 0);
+        System.out.println(maxEnemy);
+    }
+    static void combination(int start, int idx) {
+        if (idx == 3) {
+            maxEnemy = Integer.max(maxEnemy, play());
+            return;
+        }
+        for (int i = start; i < M; i++) {
+            archerCols[idx] = i;
+            combination(i + 1, idx + 1);
+        }
+    }
+
+    static int play() {
+        // 게임을 플레이 할 임시 격자판 생성
+        int[][] board = new int[N][M];
+        for (int i = 0; i < N; i++) {
+            for (int j = 0 ; j < M; j++) {
+                board[i][j] = original[i][j];
+            }
+        }
+        int total = 0;
+        do {
+            total += shoot(board);
+            moveEnemy(board);
+        } while(!isEmpty(board));
+        return total;
+    }
+
+    static void moveEnemy(int[][] board) {
+        for (int r = N-2; r > -1; r--) {
+            for (int c = 0; c < M; c++) {
+                board[r+1][c] = board[r][c];
+            }
+        }
+        // 맨 위 행은 0으로 채운다.
+        Arrays.fill(board[0], 0);
+    }
+    static int shoot(int[][] board) {
+        Set<Integer> killed = new HashSet<>();
+        for (int archerCol : archerCols) {
+            int minDist = D+1;
+            int minLoc = -1;
+            for (int r = 0; r < N; r++) {
+                for (int c = 0; c < M; c++) {
+                    if (board[r][c] == 0) continue;
+                    int dist = getDist(N, archerCol, r, c);
+                    if (dist <= D) {
+                        if (dist < minDist || (dist == minDist && c < minLoc % M)) {
+                            minDist = dist;
+                            minLoc = r * M + c;
+                        }
+                    }
+                }
+            }
+            if (minLoc == -1) { continue; }
+            killed.add(minLoc);
+        }
+
+        // 제거한 적 위치 0으로 전환
+        for (int k : killed) {
+            int kr = k / M;
+            int kc = k % M;
+            board[kr][kc] = 0;
+        }
+        return killed.size();
+    }
+
+    static boolean isEmpty(int[][] board) {
+        for (int i = 0; i < N; i++) {
+            for (int j = 0; j < M; j++) {
+                if (board[i][j] == 1) { return false; }
+            }
+        }
+        return true;
+    }
+    static int getDist(int r1, int c1, int r2, int c2) {
+        return Math.abs(r1-r2) + Math.abs(c1-c2);
+    }
+    static void input() throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+        D = Integer.parseInt(st.nextToken());
+        original = new int[N][M];
+        for (int i = 0; i < N; i++) {
+            st = new StringTokenizer(br.readLine());
+            for (int j = 0; j < M; j++) {
+                original[i][j] = Integer.parseInt(st.nextToken());
+            }
+        }
+        br.close();
+    }
+}
+
+```