feat: add python and java solutions to lcof problem

添加《剑指 Offer》题解：面试题47. 礼物的最大价值

Author: yanglbme

lcof/面试题47. 礼物的最大价值/README.md

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+# [面试题47. 礼物的最大价值](https://leetcode-cn.com/problems/li-wu-de-zui-da-jie-zhi-lcof/)
+
+## 题目描述
+在一个 `m*n` 的棋盘的每一格都放有一个礼物，每个礼物都有一定的价值（价值大于 0）。你可以从棋盘的左上角开始拿格子里的礼物，并每次向右或者向下移动一格、直到到达棋盘的右下角。给定一个棋盘及其上面的礼物的价值，请计算你最多能拿到多少价值的礼物？
+
+**示例 1:**
+
+```
+输入: 
+[
+  [1,3,1],
+  [1,5,1],
+  [4,2,1]
+]
+输出: 12
+解释: 路径 1→3→5→2→1 可以拿到最多价值的礼物
+```
+
+**提示：**
+
+- `0 < grid.length <= 200`
+- `0 < grid[0].length <= 200`
+
+## 解法
+### Python3
+```python
+class Solution:
+    def maxValue(self, grid: List[List[int]]) -> int:
+        rows, cols = len(grid), len(grid[0])
+        if rows == 0 or cols == 0:
+            return 0
+        vals = [[0 for _ in range(cols)] for _ in range(rows)]
+        vals[0][0] = grid[0][0]
+        for i in range(1, rows):
+            vals[i][0] = vals[i - 1][0] + grid[i][0]
+        for j in range(1, cols):
+            vals[0][j] = vals[0][j - 1] + grid[0][j]
+        for i in range(1, rows):
+            for j in range(1, cols):
+                vals[i][j] = grid[i][j] + max(vals[i - 1][j], vals[i][j - 1])
+        return vals[rows - 1][cols - 1]
+
+```
+
+### Java
+```java
+class Solution {
+    public int maxValue(int[][] grid) {
+        int rows = grid.length, cols = grid[0].length;
+        int[][] vals = new int[rows][cols];
+        vals[0][0] = grid[0][0];
+        for (int i = 1; i < rows; ++i) {
+            vals[i][0] = vals[i - 1][0] + grid[i][0];
+        }
+        for (int j = 1; j < cols; ++j) {
+            vals[0][j] = vals[0][j - 1] + grid[0][j];
+        }
+        for (int i = 1; i < rows; ++i) {
+            for (int j = 1; j < cols; ++j) {
+                vals[i][j] = grid[i][j] + Math.max(vals[i - 1][j], vals[i][j - 1]);
+            }
+        }
+        return vals[rows - 1][cols - 1];
+    }
+}
+```
+
+### ...
+```
+
+```

lcof/面试题47. 礼物的最大价值/Solution.java

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+class Solution {
+    public int maxValue(int[][] grid) {
+        int rows = grid.length, cols = grid[0].length;
+        int[][] vals = new int[rows][cols];
+        vals[0][0] = grid[0][0];
+        for (int i = 1; i < rows; ++i) {
+            vals[i][0] = vals[i - 1][0] + grid[i][0];
+        }
+        for (int j = 1; j < cols; ++j) {
+            vals[0][j] = vals[0][j - 1] + grid[0][j];
+        }
+        for (int i = 1; i < rows; ++i) {
+            for (int j = 1; j < cols; ++j) {
+                vals[i][j] = grid[i][j] + Math.max(vals[i - 1][j], vals[i][j - 1]);
+            }
+        }
+        return vals[rows - 1][cols - 1];
+    }
+}

lcof/面试题47. 礼物的最大价值/Solution.py

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+class Solution:
+    def maxValue(self, grid: List[List[int]]) -> int:
+        rows, cols = len(grid), len(grid[0])
+        if rows == 0 or cols == 0:
+            return 0
+        vals = [[0 for _ in range(cols)] for _ in range(rows)]
+        vals[0][0] = grid[0][0]
+        for i in range(1, rows):
+            vals[i][0] = vals[i - 1][0] + grid[i][0]
+        for j in range(1, cols):
+            vals[0][j] = vals[0][j - 1] + grid[0][j]
+        for i in range(1, rows):
+            for j in range(1, cols):
+                vals[i][j] = grid[i][j] + max(vals[i - 1][j], vals[i][j - 1])
+        return vals[rows - 1][cols - 1]