LeetCode 741. Cherry Pickup（动态规划）

题目来源：https://leetcode.com/problems/cherry-pickup/

问题描述

741. Cherry Pickup

Hard

In a 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;
• -1 means the cell contains a thorn that blocks your way.

 

Your task is to collect maximum number of cherries possible by following the rules below:

 

• Starting at the position (0, 0) and reaching (N-1, N-1) by moving right or down through valid path cells (cells with value 0 or 1);
• After reaching (N-1, N-1), returnin