You are given an n x n grid representing a field of cherries, each cell is one of three possible integers.
0 means the cell is empty, so you can pass through,1 means the cell contains a cherry that you can pick up and pass through, or-1 means the cell contains a thorn that blocks your way.Return the maximum number of cherries you can collect by following the rules below:
\n\n(0, 0) and reaching (n - 1, n - 1) by moving right or down through valid path cells (cells with value 0 or 1).(n - 1, n - 1), returning to (0, 0) by moving left or up through valid path cells.0.(0, 0) and (n - 1, n - 1), then no cherries can be collected.\n
Example 1:
\n![\"\"](\"https://assets.leetcode.com/uploads/2020/12/14/grid.jpg\")
\n\nInput: grid = [[0,1,-1],[1,0,-1],[1,1,1]]\nOutput: 5\nExplanation: The player started at (0, 0) and went down, down, right right to reach (2, 2).\n4 cherries were picked up during this single trip, and the matrix becomes [[0,1,-1],[0,0,-1],[0,0,0]].\nThen, the player went left, up, up, left to return home, picking up one more cherry.\nThe total number of cherries picked up is 5, and this is the maximum possible.\n\n\n
Example 2:
\n\n\nInput: grid = [[1,1,-1],[1,-1,1],[-1,1,1]]\nOutput: 0\n\n\n
\n
Constraints:
\n\nn == grid.lengthn == grid[i].length1 <= n <= 50grid[i][j] is -1, 0, or 1.grid[0][0] != -1grid[n - 1][n - 1] != -1Compiled with clang 11 using the latest C++ 17 standard.
Your code is compiled with level two optimization (-O2). AddressSanitizer is also enabled to help detect out-of-bounds and use-after-free bugs.
Most standard library headers are already included automatically for your convenience.
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