diff --git a/0512/BOJ/P1931/P1931_ko.java b/0512/BOJ/P1931/P1931_ko.java
index 8b13789..87273dd 100644
--- a/0512/BOJ/P1931/P1931_ko.java
+++ b/0512/BOJ/P1931/P1931_ko.java
@@ -1 +1,43 @@
+import java.util.Arrays;
+import java.util.Scanner;
 
+public class P1931_ko {
+	static class Meet implements Comparable<Meet> {
+		int s;
+		int f;
+
+		public Meet(int s, int f) {
+			this.s = s;
+			this.f = f;
+		}
+
+		@Override
+		public int compareTo(Meet o) {
+			if (this.f == o.f) // 끝나는 시간 같으면
+				return this.s - o.s; // 시작하는 시간 기준 정렬
+			return this.f - o.f;
+		}
+	}
+
+	public static void main(String[] args) {
+		Scanner sc = new Scanner(System.in);
+		int ans = 1; // 최소 회의 1개 가능
+		int N = sc.nextInt();
+		Meet[] mList = new Meet[N];
+
+		for (int i = 0; i < N; i++)
+			mList[i] = new Meet(sc.nextInt(), sc.nextInt());
+
+		Arrays.sort(mList); // 정렬
+
+		int nF = mList[0].f; // 앞 회의 끝나는 시간은 맨 앞 회의로 초기화
+		for (int i = 1; i < N; i++)
+			if (mList[i].s >= nF) { // 가능한 회의
+				nF = mList[i].f; // 끝나는 시간 변경
+				ans++;
+			}
+
+		System.out.print(ans);
+	}
+
+}
\ No newline at end of file
diff --git a/0512/BOJ/P1992/P1992_ko.java b/0512/BOJ/P1992/P1992_ko.java
index 8b13789..df71d45 100644
--- a/0512/BOJ/P1992/P1992_ko.java
+++ b/0512/BOJ/P1992/P1992_ko.java
@@ -1 +1,39 @@
+import java.util.Scanner;
 
+public class P1992_ko {
+	static String[][] pic;
+	static StringBuilder sb = new StringBuilder();
+
+	public static void main(String[] args) {
+		Scanner sc = new Scanner(System.in);
+		int N = sc.nextInt();
+		pic = new String[N][N];
+		for (int i = 0; i < N; i++)
+			pic[i] = sc.next().split("");
+
+		slice(0, 0, N);
+
+		System.out.print(sb);
+	}
+
+	static boolean check(int x, int y, int w) { // 너비 w만큼 같은 값인지 확인
+		for (int i = x; i < x + w; i++)
+			for (int j = y; j < y + w; j++)
+				if (!pic[x][y].equals(pic[i][j])) // 하나라도 아니면 false
+					return false;
+		return true;
+	}
+
+	static void slice(int x, int y, int w) {
+		if (check(x, y, w)) { // 시작점에서 너비 w만큼 같은 값인 경우
+			sb.append(pic[x][y]);
+			return;
+		}
+		sb.append("(");
+		for (int i = x; i < x + w; i += w / 2) // 4분의 1로 쪼개기
+			for (int j = y; j < y + w; j += w / 2)
+				slice(i, j, w / 2);
+		sb.append(")");
+	}
+
+}
\ No newline at end of file
diff --git a/0512/BOJ/P2178/P2178_ko.java b/0512/BOJ/P2178/P2178_ko.java
index 8b13789..ffc74a3 100644
--- a/0512/BOJ/P2178/P2178_ko.java
+++ b/0512/BOJ/P2178/P2178_ko.java
@@ -1 +1,61 @@
+import java.util.LinkedList;
+import java.util.Queue;
+import java.util.Scanner;
 
+public class P2178_ko {
+	static int[] dx = { -1, 1, 0, 0 }; // 상하좌우
+	static int[] dy = { 0, 0, -1, 1 };
+	static int[][] maze;
+	static int N;
+	static int M;
+
+	static class Point {
+		int x;
+		int y;
+
+		public Point(int x, int y) {
+			super();
+			this.x = x;
+			this.y = y;
+		}
+	}
+
+	public static void main(String[] args) {
+		Scanner sc = new Scanner(System.in);
+		N = sc.nextInt();
+		M = sc.nextInt();
+		maze = new int[N][M];
+
+		for (int i = 0; i < N; i++) {
+			String now = sc.next();
+			for (int j = 0; j < M; j++)
+				maze[i][j] = now.charAt(j) - '0';
+		}
+
+		System.out.print(bfs(new Point(0, 0)));
+	}
+
+	static int bfs(Point s) {
+		Queue<Point> q = new LinkedList<>();
+		q.add(s);
+		while (!q.isEmpty()) {
+			Point now = q.poll();
+			int x = now.x;
+			int y = now.y;
+			for (int d = 0; d < 4; d++) {
+				int nx = x + dx[d];
+				int ny = y + dy[d];
+				if (nx < 0 || nx >= N || ny < 0 || ny >= M || (nx == 0 && ny == 0))
+					continue;
+				if (maze[nx][ny] == 1) { // 아직 방문하지 않은 경우
+					q.add(new Point(nx, ny));
+					maze[nx][ny] = maze[x][y] + 1;
+				}
+			}
+
+		}
+
+		return maze[N - 1][M - 1];
+	}
+
+}
\ No newline at end of file