Here, We see Cherry Pickup LeetCode Solution. This Leetcode problem is done in many programming languages like C++, Java, JavaScript, Python, etc. with different approaches.

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Cherry Pickup LeetCode Solution

Problem Statement

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:

• 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), returning to (0, 0) by moving left or up through valid path cells.
• When passing through a path cell containing a cherry, you pick it up, and the cell becomes an empty cell 0.
• If there is no valid path between (0, 0) and (n - 1, n - 1), then no cherries can be collected.

Example 1:

Input: grid = [[0,1,-1],[1,0,-1],[1,1,1]]
Output: 5
Explanation: The player started at (0, 0) and went down, down, right right to reach (2, 2). 4 cherries were picked up during this single trip, and the matrix becomes [[0,1,-1],[0,0,-1],[0,0,0]]. Then, the player went left, up, up, left to return home, picking up one more cherry. The total number of cherries picked up is 5, and this is the maximum possible.

Example 2:
Input: grid = [[1,1,-1],[1,-1,1],[-1,1,1]]
Output: 0

Cherry Pickup LeetCode Solution C++

class Solution {
public:

    void cp1(int row, int col, vector<vector<int>>&grid, int ccsf, int &maxcc){
        
        if(row<0 || row>=grid.size() || col<0 || col>= grid[0].size() || grid[row][col]==-1) return;
        if(row==grid.size()-1 && col==grid[0].size()-1)
        {
            bottomToTop(row, col, grid, ccsf, maxcc);
        }
        
        int cherries = grid[row][col];
        grid[row][col]=0;
        
        cp1(row, col+1, grid, ccsf+cherries, maxcc);
        cp1(row+1, col, grid, ccsf+cherries, maxcc);
        grid[row][col]=cherries;
        
    }
    
    void bottomToTop(int row, int col, vector<vector<int>>&grid, int ccsf, int &maxcc){
        
        if(row<0 || row>=grid.size() || col<0 || col>= grid[0].size() || grid[row][col]==-1) return;
        if(row==0 && col==0)
        {
            maxcc = max(maxcc, ccsf);
            return;
        }

        int cherries = grid[row][col];
        grid[row][col]=0;
        
        bottomToTop(row, col-1, grid, ccsf+cherries, maxcc);
        bottomToTop(row-1, col, grid, ccsf+cherries, maxcc);
        grid[row][col]=cherries;
        
    }
    
    int cherryPickup(vector<vector<int>>& grid) {
         if(grid.size()==1 && grid[0][0]==1) return 1;
        int ccsf=0;
        int maxcc=0;
        cp1(0,0,grid,ccsf,maxcc);
        return maxcc;
    }
 
};Code language: JavaScript (javascript)

Cherry Pickup LeetCode Solution Java

class Solution {
    public int cherryPickup(int[][] grid) {
        int m = grid.length, n = grid[0].length;
        maxCherry=0;
        rd(0,0,grid,0,m,n);
        return maxCherry;
    }
    int maxCherry;
    private void rd(int x, int y, int[][] g, int cpsf, int m, int n){
        if(x>=m||y>=n||g[x][y]==-1) return;
        if(x==m-1&&y==n-1){
            int cherries=g[x][y];
            g[x][y]=0;
            lu(x,y,g,cpsf+cherries);
            g[x][y]=cherries;
            return;
        }
        int cherries = g[x][y];
        g[x][y]=0;
        rd(x+1,y,g,cpsf+cherries,m,n);
        rd(x,y+1,g,cpsf+cherries,m,n);
        g[x][y]=cherries;
    }
    
    private void lu(int x, int y, int[][] g, int cpsf){
        if(x<0||y<0||g[x][y]==-1) return;
        if(x==0&&y==0){
            maxCherry=Math.max(maxCherry,cpsf);
            return;
        }
        int cherries = g[x][y];
        g[x][y]=0;
        lu(x-1,y,g,cpsf+cherries);
        lu(x,y-1,g,cpsf+cherries);
        g[x][y]=cherries;
    }
}Code language: JavaScript (javascript)

Cherry Pickup LeetCode Solution JavaScript

var cherryPickup = function(grid) {
    let result = 0, N = grid.length, cache = {}, cherries;
    
    const solve = (x1, y1, x2, y2) => {
        if(x1 === N -1 && y1 === N-1) 
            return grid[x1][y1] !== -1 ? grid[x1][y1] : -Infinity;
        if(x1 > N -1 || y1 > N-1 || x2 > N-1 || y2 > N-1 || grid[x1][y1] === -1 ||grid[x2][y2] === -1) 
            return -Infinity;
        
        let lookup_key = `${x1}:${y1}:${x2}:${y2}`;
        if(cache[lookup_key]) return cache[lookup_key];
        
        if(x1 === x2 && y1 === y2) 
            cherries = grid[x1][y1];
        else
            cherries = grid[x1][y1] + grid[x2][y2];
        
        result = cherries + Math.max(solve(x1 + 1, y1, x2 + 1, y2),
                solve(x1, y1 + 1, x2, y2 + 1),
                solve(x1 + 1, y1, x2, y2 + 1),
                solve(x1, y1 + 1, x2 + 1, y2));
        
        cache[lookup_key] = result;
        return result;
    };
    
    result = solve(0, 0, 0, 0);
    return result > 0 ? result : 0;
};Code language: JavaScript (javascript)

Cherry Pickup LeetCode Solution Python

class Solution(object):
    
    def cherryPickup(self, grid):       
        m = len(grid)
        n = len(grid[0])
        self.cherries = 0
        self.memo = {}
        return max(0, self.dfs(grid, m, n, 0, 0, 0, 0))
        
    def dfs(self, grid, m, n, x1, y1, x2, y2):

        if (x1 >= m) or (x2 >= m) or (y1 >= n) or (y2 >= n) or \
            grid[x1][y1] == -1 or grid[x2][y2] == -1:
            return float('-inf')

        if (x1, y1, x2) not in self.memo:
            cherries = 0
            if grid[x1][y1] == 1:
                cherries += 1
            if grid[x2][y2] == 1 and x1 != x2:
                cherries += 1
            if x1 == m-1 and y1 == n-1:
                return cherries

            cherries += max(
                self.dfs(grid, m, n, x1 + 1, y1, x2 + 1, y2),
                self.dfs(grid, m, n, x1 + 1, y1, x2, y2 + 1),
                self.dfs(grid, m, n, x1, y1 + 1, x2 + 1, y2),
                self.dfs(grid, m, n, x1, y1 + 1, x2, y2 + 1),
            )
            self.memo[(x1, y1, x2)] = cherries

        return self.memo[(x1, y1, x2)]