feat: python solution, DFS

Author: sunlight0602

problems/kamacoder/0103.水流问题.md

@@ -355,6 +355,62 @@ public class Main {
 ```
 
 ### Python
+```Python
+first = set()
+second = set()
+directions = [[-1, 0], [0, 1], [1, 0], [0, -1]]
+
+def dfs(i, j, graph, visited, side):
+    if visited[i][j]:
+        return
+    
+    visited[i][j] = True
+    side.add((i, j))
+    
+    for x, y in directions:
+        new_x = i + x
+        new_y = j + y
+        if (
+            0 <= new_x < len(graph)
+            and 0 <= new_y < len(graph[0])
+            and int(graph[new_x][new_y]) >= int(graph[i][j])
+        ):
+            dfs(new_x, new_y, graph, visited, side)
+
+def main():
+    global first
+    global second
+    
+    N, M = map(int, input().strip().split())
+    graph = []
+    for _ in range(N):
+        row = input().strip().split()
+        graph.append(row)
+    
+    # 是否可到达第一边界
+    visited = [[False] * M for _ in range(N)]
+    for i in range(M):
+        dfs(0, i, graph, visited, first)
+    for i in range(N):
+        dfs(i, 0, graph, visited, first)
+    
+    # 是否可到达第二边界
+    visited = [[False] * M for _ in range(N)]
+    for i in range(M):
+        dfs(N - 1, i, graph, visited, second)
+    for i in range(N):
+        dfs(i, M - 1, graph, visited, second)
+
+    # 可到达第一边界和第二边界
+    res = first & second
+    
+    for x, y in res:
+        print(f"{x} {y}")
+    
+    
+if __name__ == "__main__":
+    main()
+```
 
 ### Go