misc: restructure contents

experimental/utilities/python/graph_dfs.py

@@ -0,0 +1,45 @@
+def graph_dfs(matrix):
+    rows, cols = len(matrix), len(matrix[0])
+    visited = set()
+    directions = ((0, 1), (0, -1), (1, 0), (-1, 0))
+    def dfs(i, j):
+        if (i, j) in visited:
+            return
+        visited.add((i, j))
+        # Traverse neighbors.
+        for direction in directions:
+            next_i, next_j = i + direction[0], j + direction[1]
+            if 0 <= next_i < rows and 0 <= next_j < cols: # Check boundary.
+                # Add any other checking here ^
+                dfs(next_i, next_j)
+
+    for i in range(rows):
+        for j in range(cols):
+            dfs(i, j)
+
+# Follow up:
+# 1) Diagonal cells are considered neighbors
+# 2) View the matrix like Earth, right boundary is adjacent to the left boundary, top adjacent to left, etc.
+def graph_dfs_diagonals_and_boundary_wrap(matrix):
+    rows, cols = len(matrix), len(matrix[0])
+    visited = set()
+    # Change 1: Add 4 more diagonal directions.
+    directions = ((0, 1), (0, -1), (1, 0), (-1, 0), (-1, -1), (1, 1), (1, -1), (-1, 1))
+    def dfs(i, j):
+        if (i, j) in visited:
+            return
+        visited.add((i, j))
+        for direction in directions:
+            # Change 2: No more boundary, use modulo to allow traversal that exceed boundaries to wrap around.
+            next_i, next_j = (i + direction[0] + rows) % rows, (j + direction[1] + cols) % cols
+            dfs(next_i, next_j)
+
+    for i in range(rows):
+        for j in range(cols):
+            dfs(i, j)
+
+graph_dfs([
+    [1, 2, 3, 4],
+    [5, 6, 7, 8],
+    [9, 10, 11, 12],
+])