1728. Cat and Mouse II

Updated: 2024-03-12
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LeetCode problem 1728

class Solution:
    def canMouseWin(self, grid: List[str], catJump: int, mouseJump: int) -> bool:
        dirs = [0, 1, 0, -1, 0]
        m = len(grid)
        n = len(grid[0])
        nFloors = 0
        cat = 0  # cat's position
        mouse = 0  # mouse's position

        def hash(i: int, j: int) -> int:
            return i * n + j

        for i in range(m):
            for j in range(n):
                if grid[i][j] != "#":
                    nFloors += 1
                if grid[i][j] == "C":
                    cat = hash(i, j)
                elif grid[i][j] == "M":
                    mouse = hash(i, j)

        # dp(i, j, k) := True if mouse can win w//
        # Cat on (i // 8, i % 8), mouse on (j // 8, j % 8), and turns = k
        @functools.lru_cache(None)
        def dp(cat: int, mouse: int, turn: int) -> bool:
            # We already search whole touchable grid
            if turn == nFloors * 2:
                return False

            if turn % 2 == 0:
                # mouse's turn
                i = mouse // n
                j = mouse % n
                for k in range(4):
                    for jump in range(mouseJump + 1):
                        x = i + dirs[k] * jump
                        y = j + dirs[k + 1] * jump
                        if x < 0 or x == m or y < 0 or y == n:
                            break
                        if grid[x][y] == "#":
                            break
                        if grid[x][y] == "F":  # Mouse eats the food, so mouse win
                            return True
                        if dp(cat, hash(x, y), turn + 1):
                            return True
                # Mouse can't win, so mouse lose
                return False
            else:
                # cat's turn
                i = cat // n
                j = cat % n
                for k in range(4):
                    for jump in range(catJump + 1):
                        x = i + dirs[k] * jump
                        y = j + dirs[k + 1] * jump
                        if x < 0 or x == m or y < 0 or y == n:
                            break
                        if grid[x][y] == "#":
                            break
                        if grid[x][y] == "F":  # Cat eats the food, so mouse lose
                            return False
                        nextCat = hash(x, y)
                        if nextCat == mouse:  # Cat catches mouse, so mouse lose
                            return False
                        if not dp(nextCat, mouse, turn + 1):
                            return False
                # Cat can't win, so mouse win
                return True

        return dp(cat, mouse, 0)