337_HouseRobberIII - a920604a/leetcode GitHub Wiki
- dfs - time out
class Solution {
public:
int robber(TreeNode* root){
if(!root) return 0;
int do_it = root->val, not_do_it=0;
if(root->left) do_it+=robber(root->left->left)+robber(root->left->right);
if(root->right) do_it+=robber(root->right->left)+robber(root->right->right);
not_do_it+=robber(root->left)+robber(root->right);
return max(do_it,not_do_it);
}
int rob(TreeNode* root) {
if(!root) return 0;
return robber(root);
}
};
memo 紀錄拜訪過的,避免重複拜訪節點
class Solution {
public:
unordered_map<TreeNode*, int> memo;
int robber(TreeNode* root){
if(!root) return 0;
int do_it = root->val, not_do_it=0;
if(memo.find(root)!=memo.end()) return memo[root];
if(root->left) do_it+=robber(root->left->left)+robber(root->left->right);
if(root->right) do_it+=robber(root->right->left)+robber(root->right->right);
not_do_it+=robber(root->left)+robber(root->right);
memo[root] = max(do_it,not_do_it);
return memo[root];
}
int rob(TreeNode* root) {
if(!root) return 0;
return robber(root);
}
};
public:
vector<int> dfs(TreeNode *root){
if(!root) return vector<int>(2,0);
vector<int> left = dfs(root->left);
vector<int> right = dfs(root->right);
vector<int> ret(2,0);
// not_do_it vs. do_it
ret[0] = max(left[0], left[1]) + max(right[0], right[1]);
ret[1] = left[0]+right[0]+root->val;
return ret;
}
int rob(TreeNode* root) {
vector<int> res = dfs(root);
return max(res[0], res[1]);
}
};