leetcode题目:house robber iii

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.

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class Solution {
public:
    int (TreeNode* root) {
        if(!root)
            return 0;
        if(NULL == root->left && NULL == root->right)
            return root->val;
        
        int c1 = rob(root->left) + rob(root->right);
        int c2 = root->val;
        if(root->left)
            c2 += rob(root->left->left) + rob(root->left->right);
        if(root->right)
            c2 += rob(root->right->left) + rob(root->right->right);
        return c1 > c2 ? c1 : c2;
    }
};