337.打家劫舍III

自己做的

/**
 * 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:
// <r1,r2> r1 如果偷当前节点，得到的最大值 ； r2 不偷当前节点的最大值
    pair<int,int> f(TreeNode*root) {
        if(!root){return make_pair(0,0);}
        auto leftr = f(root->left);
        auto rightr = f(root->right);
        int takeleft = leftr.first;
        int notakeleft = leftr.second;
        int takeright = rightr.first;
        int notakeright = rightr.second;
        int r1 = notakeleft + notakeright + root->val;
        int r2 = max(takeleft,notakeleft) + max(takeright,notakeright);
        return make_pair(r1, r2);
    }
    int rob(TreeNode* root) {
        auto res = f(root);
        return max(res.first, res.second);
    }
};