diff --git a/BOJ_16236.cpp b/BOJ_16236.cpp
new file mode 100644
index 0000000..79e84f2
--- /dev/null
+++ b/BOJ_16236.cpp
@@ -0,0 +1,108 @@
+#include <iostream>
+#include <vector>
+#include <queue>
+#include <algorithm>
+#include <tuple>
+
+using namespace std;
+
+struct Shark
+{
+  int x, y, size, eaten;
+};
+
+int N;
+vector<vector<int>> grid;
+Shark shark;
+
+const int dx[] = {-1, 1, 0, 0};
+const int dy[] = {0, 0, -1, 1};
+
+bool is_in_bounds(int x, int y)
+{
+  return x >= 0 && x < N && y >= 0 && y < N;
+}
+
+int bfs()
+{
+  vector<vector<bool>> visited(N, vector<bool>(N, false));
+  queue<tuple<int, int, int>> q;
+  q.push({shark.x, shark.y, 0});
+  visited[shark.x][shark.y] = true;
+
+  vector<tuple<int, int, int>> fish_candidates;
+
+  while (!q.empty())
+  {
+    int x, y, dist;
+    tie(x, y, dist) = q.front();
+    q.pop();
+
+    for (int i = 0; i < 4; ++i)
+    {
+      int nx = x + dx[i], ny = y + dy[i];
+
+      if (is_in_bounds(nx, ny) && !visited[nx][ny] && grid[nx][ny] <= shark.size)
+      {
+        visited[nx][ny] = true;
+        q.push({nx, ny, dist + 1});
+
+        if (grid[nx][ny] > 0 && grid[nx][ny] < shark.size)
+        {
+          fish_candidates.push_back({dist + 1, nx, ny});
+        }
+      }
+    }
+  }
+
+  if (fish_candidates.empty())
+    return 0;
+
+  sort(fish_candidates.begin(), fish_candidates.end());
+  int dist, fish_x, fish_y;
+  tie(dist, fish_x, fish_y) = fish_candidates[0];
+
+  shark.x = fish_x;
+  shark.y = fish_y;
+  shark.eaten++;
+  if (shark.eaten == shark.size)
+  {
+    shark.size++;
+    shark.eaten = 0;
+  }
+
+  grid[fish_x][fish_y] = 0;
+
+  return dist;
+}
+
+int main()
+{
+  cin >> N;
+  grid.resize(N, vector<int>(N));
+
+  for (int i = 0; i < N; ++i)
+  {
+    for (int j = 0; j < N; ++j)
+    {
+      cin >> grid[i][j];
+      if (grid[i][j] == 9)
+      {
+        shark = {i, j, 2, 0};
+        grid[i][j] = 0;
+      }
+    }
+  }
+
+  int total_time = 0;
+  while (true)
+  {
+    int time_spent = bfs();
+    if (time_spent == 0)
+      break;
+    total_time += time_spent;
+  }
+
+  cout << total_time << endl;
+  return 0;
+}
\ No newline at end of file
diff --git a/BOJ_20040.cpp b/BOJ_20040.cpp
new file mode 100644
index 0000000..928b7de
--- /dev/null
+++ b/BOJ_20040.cpp
@@ -0,0 +1,68 @@
+#include <iostream>
+#include <vector>
+using namespace std;
+
+int findParent(vector<int> &parent, int x)
+{
+  if (parent[x] != x)
+  {
+    parent[x] = findParent(parent, parent[x]);
+  }
+  return parent[x];
+}
+
+bool unionNodes(vector<int> &parent, vector<int> &rank, int a, int b)
+{
+  int rootA = findParent(parent, a);
+  int rootB = findParent(parent, b);
+
+  if (rootA == rootB)
+    return true;
+
+  if (rank[rootA] > rank[rootB])
+  {
+    parent[rootB] = rootA;
+  }
+  else if (rank[rootA] < rank[rootB])
+  {
+    parent[rootA] = rootB;
+  }
+  else
+  {
+    parent[rootB] = rootA;
+    rank[rootA]++;
+  }
+  return false;
+}
+
+int main()
+{
+  int n, m;
+  cin >> n >> m;
+
+  vector<int> parent(n);
+  vector<int> rank(n, 0);
+
+  // 초기화
+  for (int i = 0; i < n; i++)
+  {
+    parent[i] = i;
+  }
+
+  int result = 0;
+
+  for (int i = 1; i <= m; i++)
+  {
+    int a, b;
+    cin >> a >> b;
+
+    if (unionNodes(parent, rank, a, b))
+    {
+      result = i; // 사이클이 처음으로 발생한 차례
+      break;
+    }
+  }
+
+  cout << result << endl;
+  return 0;
+}
diff --git a/week13/.gitkeep b/week13/.gitkeep
new file mode 100644
index 0000000..e69de29
diff --git "a/\355\224\204\353\241\234\352\267\270\353\236\230\353\250\270\354\212\244_\353\204\244\355\212\270\354\233\214\355\201\254.cpp" "b/\355\224\204\353\241\234\352\267\270\353\236\230\353\250\270\354\212\244_\353\204\244\355\212\270\354\233\214\355\201\254.cpp"
new file mode 100644
index 0000000..c7a0a6f
--- /dev/null
+++ "b/\355\224\204\353\241\234\352\267\270\353\236\230\353\250\270\354\212\244_\353\204\244\355\212\270\354\233\214\355\201\254.cpp"
@@ -0,0 +1,33 @@
+#include <string>
+#include <vector>
+
+using namespace std;
+
+void dfs(int node, vector<vector<int>> &computers, vector<bool> &visited)
+{
+  visited[node] = true;
+  for (int i = 0; i < computers.size(); i++)
+  {
+    if (computers[node][i] == 1 && !visited[i])
+    {
+      dfs(i, computers, visited);
+    }
+  }
+}
+
+int solution(int n, vector<vector<int>> computers)
+{
+  vector<bool> visited(n, false);
+  int networkCount = 0;
+
+  for (int i = 0; i < n; i++)
+  {
+    if (!visited[i])
+    {
+      dfs(i, computers, visited);
+      networkCount++;
+    }
+  }
+
+  return networkCount;
+}
\ No newline at end of file