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Diffstat (limited to 'other/all_possible_full_tree.cpp')
-rw-r--r-- | other/all_possible_full_tree.cpp | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/other/all_possible_full_tree.cpp b/other/all_possible_full_tree.cpp new file mode 100644 index 0000000..ca54570 --- /dev/null +++ b/other/all_possible_full_tree.cpp @@ -0,0 +1,40 @@ +// 894. All Possible Full Binary Trees +#include "leetcode.h" + +/* + * given an integer 'n', return a list of all possible full binary trees with + * 'n' nodes. each node of each tree in the answer must have 'node.val == 0'. + * each element of the answer is the root node of one possible tree. you may + * return the final list of trees in any order. a full binary tree is a binary + * tree where each node has exactly zero or two children + */ + +class Solution { +public: + vector<TreeNode *> allPossibleFBT(int n) { + unordered_map<int, vector<TreeNode *>> memo; + vector<TreeNode *> ans; + if (n < 1 || !n % 2) + return ans; + if (memo.find(n) != memo.end()) + return memo[n]; + if (n == 1) { + ans.push_back(new TreeNode(0)); + memo[1] = ans; + return ans; + } + for (int i = 1; i < n; i += 2) { + vector<TreeNode *> left = allPossibleFBT(i); + vector<TreeNode *> right = allPossibleFBT(n - 1 - i); + for (int j = 0; j < left.size(); j++) + for (int k = 0; k < right.size(); k++) { + TreeNode *root = new TreeNode(0); + root->left = left[j]; + root->right = right[k]; + ans.push_back(root); + } + } + memo[n] = ans; + return ans; + } +}; |