力扣第95题 不同的二叉搜索树II

力扣第95题 不同的二叉搜索树II

给定一个整数 n，生成所有由 1 ... n 为节点所组成的二叉搜索树。

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};

 vector<TreeNode*> generateTree(int start, int end)
 {
     vector<TreeNode*> vect;
     if (start > end)
     {
         vect.push_back(NULL);
         return vect;
     }
     for (int i = start; i <= end; i++)
     {
         vector<TreeNode*> left = generateTree(start, i - 1);
         vector<TreeNode*> right = generateTree(i + 1, end);
         for (vector<TreeNode*>::iterator itorl = left.begin(); itorl != left.end(); itorl++)
         {
             for (vector<TreeNode*>::iterator itorr = right.begin(); itorr != right.end(); itorr++)
             {
                 TreeNode* pNode = new TreeNode(i);
                 pNode->left = *itorl;
                 pNode->right = *itorr;
                 vect.push_back(pNode);
             }
         }
     }
     return vect;
 }

 vector<TreeNode*> generateTrees(int n) 
 {
     vector<TreeNode*> vect;
     if (n <= 0)
     {
         return vect;
     }
     return generateTree(1, n);
 }