Merge pull request #582 from AlgorithmWithGod/0224LJH

[20250731] BOJ / G4 /  / 이종환

Author: ShinHeeEul

0224LJH/202507/31 BOJ 뱀 .md

@@ -0,0 +1,111 @@
+```java
+import java.awt.Point;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.util.LinkedList;
+import java.util.Queue;
+import java.util.Stack;
+import java.util.StringTokenizer;
+
+
+public class Main {
+
+    static final int APPLE = -1;
+    static final int EMPTY = 0;
+    static final int SNAKE = 1;
+
+    static Change[] change;
+    static Queue<Point> snake;
+
+    static int[][] arr;
+    static int[] dy = {0,1,0,-1}; // 오른쪽->아래->왼쪽->위
+    static int[] dx = {1,0,-1,0};
+    static int size,appleCnt,changeCnt,direction,cur;
+
+    static class Change{
+        int time;
+        int direction;
+        public Change(int time, int direction){
+            this.time = time;
+            this.direction = direction;
+        }
+    }
+
+
+    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));
+        snake = new LinkedList<>();
+        size = Integer.parseInt(br.readLine());
+        appleCnt = Integer.parseInt(br.readLine());
+        direction = 0;
+        snake.add(new Point(0,0));
+
+        arr = new int[size][size];
+
+        for (int i = 0; i < appleCnt; i++) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            int y = Integer.parseInt(st.nextToken())-1;
+            int x = Integer.parseInt(st.nextToken())-1;
+            arr[y][x] = APPLE;
+        }
+
+        changeCnt = Integer.parseInt(br.readLine());
+        change = new Change[changeCnt];
+        for (int i = 0; i < changeCnt; i++) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            int time = Integer.parseInt(st.nextToken());
+            int direction = (st.nextToken().equals("L"))?-1:1;
+            change[i] = new Change(time, direction);
+        }
+    }
+
+    private static void process() throws IOException {
+        Point head = snake.peek();
+        cur = 0;
+        int changeIdx= 0;
+
+        while (true) {
+            cur++;
+            int ny =  head.y + dy[direction];
+            int nx = head.x +  dx[direction];
+
+            if (ny < 0 || nx < 0 || ny >= size || nx >= size) break;
+            if (arr[ny][nx] == SNAKE) break;
+
+            Point nHead = new Point(nx, ny);
+
+            snake.add(nHead);
+            if (arr[ny][nx] == EMPTY) {
+                Point tail = snake.poll();
+                arr[tail.y][tail.x] = EMPTY;
+            }
+            //사과를 만난경우 그냥 진행하면됨
+
+            arr[ny][nx] = SNAKE;
+
+            head = nHead;
+
+            if (changeIdx < changeCnt) {
+                Change c =  change[changeIdx];
+                if (cur < c.time) continue;
+
+                direction = (direction +  c.direction + 4)%4 ;
+                changeIdx++;
+            }
+
+        }
+
+    }
+
+    private static void print() {
+        System.out.println(cur);
+    }
+}
+```