Update:抢房子 C++版本

Author: 5ooo

动态规划系列/抢房子.md

@@ -230,9 +230,122 @@ int[] dp(TreeNode root) {
 
 ![labuladong](../pictures/labuladong.jpg)
 
+[5ooo](https://github.com/5ooo) 提供 House Robber I C++ 解法代码：
+
+```c++
+class Solution {
+public:
+    int rob(vector<int>& nums) {
+        int dp_i = 0;   //第i间房子最多能抢的钱
+        int dp_i_1 = 0; //第i+1间房子最多能抢的钱
+        int dp_i_2 = 0; //第i+2间房子最多能抢的钱
+
+        //从最后一间房子开始，往前移动
+        for (int i = nums.size() - 1; i >= 0; i--) {
+            dp_i = max(dp_i_1, nums[i] + dp_i_2);
+            dp_i_2 = dp_i_1;
+            dp_i_1 = dp_i;
+        }
+    
+        return dp_i;
+    }
+};
+```
+
+[5ooo](https://github.com/5ooo) 提供 House Robber II C++ 解法代码：
+
+```c++
+class Solution {
+public:
+    int rob(vector<int>& nums) {
+        if (nums.size() == 1)
+            return nums[0];
+
+        return max(robRange(nums, 0, nums.size() - 2),
+                   robRange(nums, 1, nums.size() - 1));
+    }
+    
+    int robRange(vector<int>& nums, int start, int end) {
+        int dp_i = 0;   //第i间房子最多能抢的钱
+        int dp_i_1 = 0; //第i+1间房子最多能抢的钱
+        int dp_i_2 = 0; //第i+2间房子最多能抢的钱
+    
+        for (int i = end; i >= start; i--) {
+            dp_i = max(dp_i_1, nums[i] + dp_i_2);
+            dp_i_2 = dp_i_1;
+            dp_i_1 = dp_i;
+        }
+    
+        return dp_i;
+    }
+};
+```
+
+[5ooo](https://github.com/5ooo) 提供 House Robber III C++ 解法代码：
+
+```c++
+class Solution {
+public:
+    int rob(TreeNode* root) {
+        if (root == nullptr)
+            return 0;
+
+        // 利用备忘录消除重叠子问题
+        if (memo.find(root) != memo.end())
+            return memo[root];
+    
+        // 抢，然后去下下家
+        int do_it = root->val + 
+                    (root->left == nullptr ? 
+                    0 : rob(root->left->left) + rob(root->left->right)) + 
+                    (root->right == nullptr ? 
+                    0 : rob(root->right->left) + rob(root->right->right));
+        
+        // 不抢，然后去下家
+        int not_do = rob(root->left) + rob(root->right);
+    
+        int ret = max(do_it, not_do);
+        memo[root] = ret;
+    
+        return ret;
+    }
+private:
+    unordered_map<TreeNode *, int > memo;
+};
+```
+
+```c++
+class Solution {
+public:
+    int rob(TreeNode* root) {
+        //ret[0]表示不抢root,获取的最大钱数
+        //ret[1]表示抢root,获取的最大钱数
+        vector<int> ret = dp(root);
+        return max(ret[0], ret[1]);
+    }
+    
+
+    vector<int> dp(TreeNode* root) {
+        if (root == nullptr) 
+            return {0, 0};
+        
+        vector<int> left = dp(root->left); 
+        vector<int> right = dp(root->right);
+        
+        //抢当前的，则接下来不能抢
+        int rob = root->val + left[0] + right[0];
+        
+        //不抢当前的，接下来可抢可不抢，取收益大的
+        int not_rob = max(left[0], left[1]) + max(right[0], right[1]);
+        
+        return {not_rob, rob};
+    }
+};
+```
 
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-[目录](../README.md#目录)
+[目录](../README.md#目录)
+