Create 329-Longest-Increasing-Path-in-a-Matrix.py

Author: neetcode-gh

329-Longest-Increasing-Path-in-a-Matrix.py

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+class Solution:
+    def longestIncreasingPath(self, matrix: List[List[int]]) -> int:
+        ROWS, COLS = len(matrix), len(matrix[0])
+        dp = {} # (r, c) -> LIP
+        
+        def dfs(r, c, prevVal):
+            if (r < 0 or r == ROWS or
+                c < 0 or c == COLS or
+                matrix[r][c] <= prevVal):
+                return 0
+            if (r, c) in dp:
+                return dp[(r, c)]
+            
+            res = 1
+            res = max(res, 1 + dfs(r + 1, c, matrix[r][c]))
+            res = max(res, 1 + dfs(r - 1, c, matrix[r][c]))
+            res = max(res, 1 + dfs(r, c + 1, matrix[r][c]))
+            res = max(res, 1 + dfs(r, c - 1, matrix[r][c]))
+            dp[(r, c)] = res
+            return res
+
+        for r in range(ROWS):
+            for c in range(COLS):
+                dfs(r, c, -1)
+        return max(dp.values())