Merge pull request #350 from MoigeMatino/add-best-bridge-v3

feat: add best bridge v3

Author: MoigeMatino

graphs/best_bridge/best_bridge_v3.py

@@ -0,0 +1,71 @@
+from typing import List, Set, Tuple
+from collections import deque
+
+def best_bridge(grid: List[List]) -> int:
+    visited = set()
+    
+    for r in range(len(grid)):
+        for c in range(len(grid[0])):
+            island = find_island(grid, r, c, visited)
+            if len(island) > 0:
+                break
+        if len(island) > 0:
+            first_island = island
+            break
+        
+    if len(island) == 0:
+        return "No island in sight"
+    
+    queue = deque([])
+    for pos in first_island:
+        r, c = pos
+        queue.append((r, c, 0))
+        
+    newly_visited = set()
+    
+    while queue:
+        curr_r, curr_c, distance = queue.popleft()
+        curr_pos = curr_r, curr_c
+        
+        if grid[curr_r][curr_c] == "L" and curr_pos not in first_island:
+            return distance - 1
+        
+        deltas = deltas = [(1, 0), (-1, 0), (0, 1), (0, -1)]  #  Possible directions to move in the grid
+        for delta in deltas:
+            delta_r, delta_c = delta
+            neighbor_r = delta_r + curr_r
+            neighbor_c = delta_c + curr_c
+            neighbor_pos = neighbor_r, neighbor_c
+            if inbounds(grid, neighbor_r, neighbor_c) and neighbor_pos not in newly_visited:
+                newly_visited.add(neighbor_pos)
+                queue.append((neighbor_r, neighbor_c, distance + 1))
+    return -1    
+
+
+def find_island(grid: List[List], r: int, c: int, visited: Set[Tuple]) -> bool:
+    queue = deque([(r,c)])
+    
+    while queue:
+        curr_r, curr_c = queue.popleft()
+        curr_pos = curr_r, curr_c
+        
+        if grid[curr_r][curr_c] == "W" or curr_pos in visited:
+            continue
+        
+        visited.add(curr_pos)
+        deltas = deltas = [(1, 0), (-1, 0), (0, 1), (0, -1)]  #  Possible directions to move in the grid
+        for delta in deltas:
+            delta_r, delta_c = delta
+            neighbor_r = delta_r + r
+            neighbor_c = delta_c + c
+            if inbounds(grid, neighbor_r, neighbor_c):
+                queue.append((neighbor_r, neighbor_c))
+                
+    return visited
+
+def inbounds(grid: List[List], r: int, c: int) -> bool:
+    row_inbounds = 0 <= r < len(grid)
+    col_inbounds = 0 <= c < len(grid[0])
+
+    return row_inbounds and col_inbounds
+