代码随想录：打家劫舍三

记忆化搜索

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left),
 * right(right) {}
 * };
 */
class Solution {
public:
    unordered_map<TreeNode*, int> umap;
    int rob(TreeNode* root) {
        if (root == NULL)
            return 0;
        if (root->left == NULL && root->right == NULL)
            return root->val;
        if (umap[root])
            return umap[root];
        // 偷当前节点
        int val1 = root->val;
        if(root->left!=NULL)val1 += rob(root->left->left) + rob(root->left->right);
        if(root->right!=NULL)val1 += rob(root->right->left) + rob(root->right->right);

        //不偷当前节点
        int val2 = rob(root->left)+rob(root->right);

        umap[root] = max(val1,val2);

        return max(val1,val2);
    }
};