feat(algs): add flood fill (steps buggy)

Author: jessicayung

algorithms/flood_fill.py

@@ -0,0 +1,59 @@
+"""
+Flood Fill
+
+Jessica Yung
+Jan 2018
+"""
+import numpy as np
+
+class FloodFill2D:
+
+    def __init__(self, grid_width, grid_height, visited=None):
+        self.grid_width = grid_width
+        self.grid_height = grid_height
+        if visited is None:
+            self.visited = np.zeros((grid_height, grid_width))
+        else:
+            self.visited = visited
+        self.steps_taken = np.zeros((grid_height, grid_width))
+
+
+    def flood_fill(self, x, y, steps=0):
+        """Basic flood fill algorithm that visits every cell in a 2D grid, where adjacent cells are defined as up to eight cells next to the current cell (can move diagonally).
+        DFS-based implementation.
+        """
+        print("Current cell: ", x, y)
+        print("Steps taken at start", self.steps_taken)
+        print("Visited at start: ", self.visited)
+        print("Steps at start: ", steps)
+        if x >= self.grid_width or y >= self.grid_height:
+            return
+        if x < 0 or y < 0:
+            return
+        if self.visited[y][x]:
+            print("Already visited ", x, y)
+            return
+
+        # Mark current cell as visited
+        self.visited[y][x] = True
+        self.steps_taken[y][x] = steps
+        print("Visited ", x, y, "in ", steps, " steps")
+        print(self.steps_taken)
+        print("Visited is now")
+        print(self.visited)
+
+        # Visit every neighbouring cell
+        for cell in self.neighbour(x, y):
+            self.flood_fill(cell[0], cell[1], steps+1)
+
+    def neighbour(self, x, y):
+        neighbours = []
+        for dx in [-1,0,1]:
+            for dy in [-1,0,1]:
+                neighbours.append([x + dx, y + dy])
+        return neighbours
+
+ff = FloodFill2D(4, 3)
+ff.flood_fill(1,2)
+print(ff.steps_taken)
+