337. House Robber III(unsolved)

The thief has found himself a new place for his thievery again. There is only one entrance to this area, called the “root.” Besides the root, each house has one and only one parent house. After a tour, the smart thief realized that “all houses in this place forms a binary tree”. It will automatically contact the police if two directly-linked houses were broken into on the same night.

Determine the maximum amount of money the thief can rob tonight without alerting the police.

Example 1:
3
/ \
2 3
\ \
3 1
Maximum amount of money the thief can rob = 3 + 3 + 1 = 7.
Example 2:
3
/ \
4 5
/ \ \
1 3 1
Maximum amount of money the thief can rob = 4 + 5 = 9.

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    int tryrob(TreeNode* root,int& l,int& r)    {        if(root==NULL) return 0;        int ll=0,lr=0,rl=0,rr=0;        l=tryrob(root->left,ll,lr);        r=tryrob(root->right,rl,rr);        return max(root->val+ll+lr+rl+rr,l+r);    }    int rob(TreeNode* root) {        int l=0,r=0;        return tryrob(root,l,r);    }};