[20250722] BOJ / G4 / 거울 / 이종환

Author: 0224LJH

0224LJH/202507/22 BOJ 거울 .md

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+```java
+import java.awt.Point;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.*;
+
+public class Main {
+
+    //거울 만날 시 진행 방향
+    //오른쪽 <-> 위
+    // 아래 <-> 왼쪽
+
+    static final int MIRROR = -1;
+
+    static int height,width,direction;
+    static int [][] arr;
+    static int[] dy = {1,0,-1,0}; // 아래 오른쪽 위쪽 왼쪽 순
+    static int[] dx = {0,1,0,-1};
+    static int[] ans;
+
+    static HashMap<Integer, Point> map = new HashMap<>();
+
+    public static void main(String[] args) throws IOException {
+        init();
+        process();
+        print();
+    }
+
+    private static void init() throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        height = Integer.parseInt(st.nextToken());
+        width = Integer.parseInt(st.nextToken());
+        arr = new int[height+2][width+2];
+        ans = new int[height*2 + width*2+1];
+
+        for (int i = 1; i <= height; i++) {
+            st = new StringTokenizer(br.readLine());
+            for (int j = 1; j <= width; j++) {
+                arr[i][j] = Integer.parseInt(st.nextToken()) * (-1);
+            }
+        }
+
+    }
+
+    private static void process() throws IOException {
+        markHoleNumber();
+        for (int i = 1; i < ans.length; i++) {
+            if (ans[i] != 0) continue;
+            Point p = map.get(i);
+
+            if (p.x == 0) direction = 1; //오른쪽으로
+            else if (p.y == height+1)  direction = 2; //위로
+            else if (p.x == width+1) direction = 3; //왼쪽으로
+            else direction = 0; // 아래로
+
+            processLightMove(i);
+        }
+
+
+
+    }
+
+    private static void processLightMove(int pointNum) {
+        Point p = map.get(pointNum);
+        int y = p.y;
+        int x = p.x;
+
+        while (true) {
+            y += dy[direction];
+            x += dx[direction];
+
+            if (arr[y][x] > 0) {
+                ans[pointNum] = arr[y][x];
+                ans[ans[pointNum]] = pointNum;
+                break;
+            }
+
+            if (arr[y][x] == MIRROR){
+                switch (direction) {
+                    case 0: direction = 3; break;
+                    case 1: direction = 2; break;
+                    case 2: direction = 1; break;
+                    case 3: direction = 0; break;
+                }
+            }
+
+
+        }
+    }
+
+    private static void markHoleNumber() {
+        // 구멍 번호 마킹
+        direction = 0;
+        int num = 1;
+        int y = 1;
+        int x = 0;
+        while ( y != 0 || x != 0){
+            if ( (y == height +1 || y == 0) && (x == 0 || x == width + 1) ) {
+                direction++;
+            } else{
+                map.put(num,new Point(x,y));
+                arr[y][x] = num++;
+            }
+
+            y += dy[direction];
+            x += dx[direction];
+        }
+
+    }
+
+
+    private static void print() {
+        for (int i = 1; i < ans.length; i++) {
+            System.out.print(ans[i] + " ");
+        }
+    }
+}
+
+```