feat(work): implement Pacific Atlantic Water Flow solution

work/1/Medium/Array/417.pacific-atlantic-water-flow.py

@@ -24,7 +24,7 @@ Return a 2D list of grid coordinates result where result[i] = [ri,
 ci] denotes that rain water can flow from cell (ri, ci) to both the
 Pacific and Atlantic oceans.
 
- 
+
 
 Example 1:
 
@@ -33,19 +33,19 @@ Input: heights =
 Output: [[0,4],[1,3],[1,4],[2,2],[3,0],[3,1],[4,0]]
 Explanation: The following cells can flow to the Pacific and Atlantic
 oceans, as shown below:
-[0,4]: [0,4] -> Pacific Ocean 
+[0,4]: [0,4] -> Pacific Ocean
        [0,4] -> Atlantic Ocean
-[1,3]: [1,3] -> [0,3] -> Pacific Ocean 
+[1,3]: [1,3] -> [0,3] -> Pacific Ocean
        [1,3] -> [1,4] -> Atlantic Ocean
-[1,4]: [1,4] -> [1,3] -> [0,3] -> Pacific Ocean 
+[1,4]: [1,4] -> [1,3] -> [0,3] -> Pacific Ocean
        [1,4] -> Atlantic Ocean
-[2,2]: [2,2] -> [1,2] -> [0,2] -> Pacific Ocean 
+[2,2]: [2,2] -> [1,2] -> [0,2] -> Pacific Ocean
        [2,2] -> [2,3] -> [2,4] -> Atlantic Ocean
-[3,0]: [3,0] -> Pacific Ocean 
+[3,0]: [3,0] -> Pacific Ocean
        [3,0] -> [4,0] -> Atlantic Ocean
-[3,1]: [3,1] -> [3,0] -> Pacific Ocean 
+[3,1]: [3,1] -> [3,0] -> Pacific Ocean
        [3,1] -> [4,1] -> Atlantic Ocean
-[4,0]: [4,0] -> Pacific Ocean 
+[4,0]: [4,0] -> Pacific Ocean
        [4,0] -> Atlantic Ocean
 Note that there are other possible paths for these cells to flow to
 the Pacific and Atlantic oceans.
@@ -57,19 +57,53 @@ Output: [[0,0]]
 Explanation: The water can flow from the only cell to the Pacific and
 Atlantic oceans.
 
- 
+
 
 Constraints:
 
-	• m == heights.length
+        • m == heights.length
 
-	• n == heights[r].length
+        • n == heights[r].length
 
-	• 1 <= m, n <= 200
+        • 1 <= m, n <= 200
 
-	• 0 <= heights[r][c] <= 10^5
+        • 0 <= heights[r][c] <= 10^5
 """
 
+
 class Solution:
     def pacificAtlantic(self, heights: list[list[int]]) -> list[list[int]]:
-        
+        rows, cols = len(heights), len(heights[0])
+        pac, atl = set(), set()
+
+        def dfs(r, c, seen, prevHeight):
+            if (
+                (r, c) in seen
+                or r < 0
+                or c < 0
+                or r == rows
+                or c == cols
+                or heights[r][c] < prevHeight
+            ):
+                return
+            seen.add((r, c))
+            dfs(r + 1, c, seen, heights[r][c])
+            dfs(r - 1, c, seen, heights[r][c])
+            dfs(r, c + 1, seen, heights[r][c])
+            dfs(r, c - 1, seen, heights[r][c])
+
+        for c in range(cols):
+            dfs(0, c, pac, heights[0][c])
+            dfs(rows - 1, c, atl, heights[rows - 1][c])
+
+        for r in range(rows):
+            dfs(r, 0, pac, heights[r][0])
+            dfs(r, cols - 1, atl, heights[r][cols - 1])
+
+        res = []
+        for r in range(rows):
+            for c in range(cols):
+                if (r, c) in pac and (r, c) in atl:
+                    res.append([r, c])
+
+        return res