diff --git a/code_study/Baekjoon/python/2239.py b/code_study/Baekjoon/python/2239.py
new file mode 100644
index 0000000..d2d7a15
--- /dev/null
+++ b/code_study/Baekjoon/python/2239.py
@@ -0,0 +1,49 @@
+import sys
+input = sys.stdin.readline
+
+board = []
+emptyAxis = []
+
+row_check = [[False]*10 for _ in range(9)]
+col_check = [[False]*10 for _ in range(9)]
+square_check = [[False]*10 for _ in range(9)]
+
+def square_idx(r, c) :
+    return (r//3)*3 + c//3
+    
+def backTracking(depth) :
+    if depth == len(emptyAxis) :
+        for row in board :
+            print("".join(map(str, row)))
+        exit(0)
+    
+    row, col = emptyAxis[depth]
+    sqr_idx = square_idx(row, col)
+    
+    for num in range(1, 10) :
+        if not row_check[row][num] and not col_check[col][num] and not square_check[sqr_idx][num] :
+            board[row][col] = num
+            row_check[row][num] = True
+            col_check[col][num] = True
+            square_check[sqr_idx][num] = True
+            
+            backTracking(depth+1)
+            
+            board[row][col] = 0
+            row_check[row][num] = False
+            col_check[col][num] = False
+            square_check[square_idx(row, col)][num] = False
+
+for i in range(9) :
+    row = list(map(int, list(input().strip())))
+    board.append(row)
+    for j in range(9) :
+        num = row[j]
+        if num == 0 :
+            emptyAxis.append((i,j))
+        else :
+            row_check[i][num] = True
+            col_check[j][num] = True
+            square_check[square_idx(i,j)][num] = True
+
+backTracking(0)
\ No newline at end of file
diff --git a/code_study/Baekjoon/python/2252.py b/code_study/Baekjoon/python/2252.py
new file mode 100644
index 0000000..fbf72f2
--- /dev/null
+++ b/code_study/Baekjoon/python/2252.py
@@ -0,0 +1,29 @@
+import heapq
+import sys
+input = sys.stdin.readline
+
+N, M = map(int, input().split())
+
+graph = [[] for _ in range(N+1)]
+inDegree = [0]*(N+1)
+for _ in range(M) :
+    u, v = map(int, input().split())
+    graph[u].append(v)
+    inDegree[v] += 1
+
+pq = []
+for i in range(1,N+1) :
+    if inDegree[i] == 0 :
+        heapq.heappush(pq, i)
+        
+result = []
+while len(pq) :
+    current = heapq.heappop(pq)
+    result.append(str(current))
+    
+    for next in graph[current] :
+        inDegree[next] -= 1
+        if inDegree[next] == 0 :
+            heapq.heappush(pq, next)
+
+print(" ".join(result))
\ No newline at end of file