Unique Binary Search Trees II
Given n, generate all structurally unique BST's (binary search trees) that store values 1...n.
For example,
Given n = 3, your program should return all 5 unique BST's shown below.
1 3 3 2 1
\ / / / \ \
3 2 1 1 3 2
/ / \ \
2 1 2 3
confused what "{1,#,2,3}" means > read more on how binary tree is serialized on OJ.
DFS罗列所有可能情况：
/**
* Definition for binary tree
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
vector
generate(int start,int end){
vector
result; if(start>end){ result.push_back(NULL); return result; } for(int i=start;i<=end;i++){ vector
left=generate(start,i-1); vector
right=generate(i+1,end); for(int j=0;j
left=left[j]; root->right=right[k]; result.push_back(root); } } return result; } vector
generateTrees(int n) { return generate(1,n); } };