LeetCode337. House Robber III
2016-03-23 20:34
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题目:
https://leetcode.com/problems/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.
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.
思路:
题意:不能连续抢直接相连的两个节点。即例2中,抢了3就不能抢4,5。问最多能抢好多。给一个二叉树,求它不直接相连的节点的val和最大为多少。
如果抢了当前节点,那么它的左右孩子就肯定不能抢了。
如果没有抢当前节点,左右孩子抢不抢取决于左右孩子的孩子的val大小。
QAQ,思路是这样。代码是参考别人的,自己没写出来……
代码:
/** * 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: vector<int> dfs(TreeNode* root){ vector<int> res(2,0);//res[0]代表抢,res[1]不抢 if(root==NULL){ return res; } vector<int> lRes=dfs(root->left); vector<int> rRes=dfs(root->right); res[0]=lRes[1]+rRes[1]+root->val;//抢当前节点,那么左右孩子就一定不能抢 res[1]=max(lRes[0],lRes[1])+max(rRes[0],rRes[1]);//不抢当前节点,左右孩子可抢可不抢 return res; } int rob(TreeNode* root) { vector<int> res=dfs(root); return max(res[0],res[1]); } };
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