cherry pickup in dp

imp dp problem

Author: dhruvkud13

C++/DP-cherryPickup.cpp

@@ -0,0 +1,105 @@
+class Solution
+{
+private:
+    int maxCherry(int i, int j1, int j2, vector<vector<int>> &grid, vector<vector<vector<int>>> &dp)
+    {
+        int n = grid.size();
+        int m = grid[0].size();
+
+        if (j1 < 0 || j2 < 0 || j1 >= m || j2 >= m)
+        {
+            return -1e8;
+        }
+        if (dp[i][j1][j2] != -1)
+            return dp[i][j1][j2];
+        if (i == n - 1)
+        {
+            if (j1 == j2)
+                return grid[i][j1];
+            else
+            {
+                return grid[i][j1] + grid[i][j2];
+            }
+        }
+
+        int maxi = -1e8;
+        for (int dj1 = -1; dj1 <= 1; dj1++)
+        {
+            for (int dj2 = -1; dj2 <= 1; dj2++)
+            {
+
+                int value = 0;
+                if (j1 == j2)
+                    value = grid[i][j2];
+                else
+                {
+                    value = grid[i][j2] + grid[i][j1];
+                }
+
+                value += maxCherry(i + 1, j1 + dj1, j2 + dj2, grid, dp);
+                maxi = max(maxi, value);
+            }
+        }
+        return dp[i][j1][j2] = maxi;
+    }
+
+public:
+    int cherryPickup(vector<vector<int>> &grid)
+    {
+        // int dp[r][c][c];
+        int n = grid.size();
+        int m = grid[0].size();
+
+        vector<vector<vector<int>>> dp(n, vector<vector<int>>(m, vector<int>(m, 0)));
+
+        for (int j1 = 0; j1 < m; j1++)
+        {
+            for (int j2 = 0; j2 < m; j2++)
+            {
+                if (j1 == j2)
+                    dp[n - 1][j1][j2] = grid[n - 1][j1];
+                else
+                {
+                    dp[n - 1][j1][j2] = grid[n - 1][j1] + grid[n - 1][j2];
+                }
+            }
+        }
+
+        for (int i = n - 2; i >= 0; i--)
+        {
+            for (int j1 = 0; j1 < m; j1++)
+            {
+                for (int j2 = 0; j2 < m; j2++)
+                {
+                    int maxi = -1e8;
+                    for (int dj1 = -1; dj1 <= 1; dj1++)
+                    {
+                        for (int dj2 = -1; dj2 <= 1; dj2++)
+                        {
+
+                            int value = 0;
+                            if (j1 == j2)
+                                value = grid[i][j2];
+                            else
+                            {
+                                value = grid[i][j2] + grid[i][j1];
+                            }
+                            if (j1 + dj1 >= 0 && j1 + dj1 < m && j2 + dj2 >= 0 && j2 + dj2 < m)
+                            {
+                                value += dp[i + 1][j1 + dj1][j2 + dj2];
+                            }
+                            else
+                            {
+                                value += -1e8;
+                            }
+                            maxi = max(maxi, value);
+                        }
+                    }
+                    dp[i][j1][j2] = maxi;
+                }
+            }
+        }
+        // return maxCherry(0,0,m-1,grid,dp);
+        return dp[0][0][m - 1];
+    }
+};