[Leetcode] Unique Binary Search Trees II

Title: (DP)

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.

Exercises

Reference Http://www.tuicool.com/articles/JJVbA3U

  PublicArraylist<treenode> Generatetrees (intN) {//Start Typing your Java solution below//Do not write main () function        returnGeneratetrees (1, N); }         PublicArraylist<treenode> Generatetrees (intAintb) {ArrayList<TreeNode> res =NewArraylist<treenode>(); if(a>b) {Res.add (NULL); }Else if(a==C) {Res.add (NewTreeNode (a)); }Else if(a<b) {             for(inti=a;i<=b;i++) {ArrayList<TreeNode> Temp1 = generatetrees (a,i-1); ArrayList<TreeNode> Temp2 = generatetrees (i+1, B);  for(TreeNode n:temp1) { for(TreeNode m:temp2) {TreeNode temp=NewTreeNode (i); Temp.left=N; Temp.right=m;                    Res.add (temp); }                }            }        }         returnRes; }

This problem is more difficult than 1 is not the number of returns, but the return of all results. Referring to code Ganker (http:1,2,3,4,.. N, BST builds on the following principles are unique: a tree with I as the root node, the left subtree is composed of [1, I1], and its right subtree is [i+1, n] constitute.    The code is as follows:    

[Leetcode] Unique Binary Search Trees II