Adding Swim In Rising Water Problem LeetCode #776 (haoel#269)

Author: ektedar

README.md

@@ -196,6 +196,7 @@ LeetCode
 |830|[Positions of Large Groups](https://leetcode.com/problems/positions-of-large-groups/) | [Python](./algorithms/python/PositionsOfLargeGroups/largeGroupPositions.py)|Easy|
 |820|[Short Encoding of Words](https://leetcode.com/problems/short-encoding-of-words/) | [C++](./algorithms/cpp/shortEncodingOfWords/ShortEncodingOfWords.cpp)|Medium|
 |804|[Unique Morse Code Words](https://leetcode.com/problems/unique-morse-code-words/description/) | [C++](./algorithms/cpp/uniqueMorseCodeWords/UniqueMorseCodeWords.cpp)|Easy|
+|776|[Swim In Rising Water](https://leetcode.com/problems/swim-in-rising-water/description/) | [Python](./algorithms/python/SwimInRisingWater/swim_in_rising_water.py)|Hard|
 |771|[Jewels and Stones](https://leetcode.com/problems/jewels-and-stones/description) | [C++](./algorithms/cpp/jewelsAndStones/JewelsAndStones.cpp)|Easy|
 |747|[Largest Number At Least Twice of Others](https://leetcode.com/problems/largest-number-at-least-twice-of-others/) | [Python](./algorithms/python/LargestNumberAtLeastTwiceOfOthers/dominantIndex.py)|Easy|
 |746|[Min Cost Climbing Stairs](https://leetcode.com/problems/min-cost-climbing-stairs/) | [C++](./algorithms/cpp/minCostClimbingStairs/MinCostClimbingStairs.cpp), [Python](./algorithms/python/MinCostClimbingStairs/minCostClimbingStairs.py)|Easy|

algorithms/python/SwimInRisingWater/swim_in_rising_water.py

@@ -0,0 +1,41 @@
+"""
+Solution to LeetCode problem Swim in Rising Water (#778)
+Difficulty: Hard
+
+Explanation:
+We are approaching the problem through Djikstras Algorith. Essentially a BFS but with a minimum heap. The neighbors that you are adding into the queue, you are only popping the minimum value neighbor. Amongst those popped value you are checking if that value is the max value seen so far. If it is, then you have found the solution.
+"""
+from heapq import heappush, heappop
+from typing import List
+
+class Solution:
+    def swimInWater(self, grid: List[List[int]]) -> int:
+        src, dst = grid[0][0], grid[len(grid)-1][len(grid)-1]
+        visited = set()
+        heap_queue = [(src, 0, 0)]  # src, row, col
+        output = 0
+        directions = [(0, 1), (1, 0), (-1, 0), (0, -1)]
+        while heap_queue:
+            current, row, col = heappop(heap_queue)
+            output = max(current, output)
+
+            # if we already hit the destination, break out of the loop
+            if current == dst:
+                break
+
+            for x, y in directions:
+                dx, dy = row+x, col+y
+                if self.check_bounds(dx, dy, grid) and (dx, dy) not in visited:
+                    heappush(heap_queue, (grid[dx][dy], dx, dy))
+                    visited.add((dx, dy))
+        return output
+
+    def check_bounds(self, r, c, grid) -> bool:
+        if 0 <= r < len(grid[0]) and 0 <= c < len(grid):
+            return True
+        return False
+
+
+if __name__ == "__main__":
+    grid = [[0, 2], [1, 3]]
+    print(Solution().swimInWater(grid))