力扣算法题—095不同的二叉搜索树【二叉树】

╰+攻爆jí腚メ 2022-01-06 00:01 227阅读 0赞

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。

示例:

输入: 3
    输出:
    [
      [1,null,3,2],
      [3,2,null,1],
      [3,1,null,null,2],
      [2,1,3],
      [1,null,2,null,3]
    ]
    解释:
    以上的输出对应以下 5 种不同结构的二叉搜索树：
    
       1         3     3      2      1
        \       /     /      / \      \
         3     2     1      1   3      2
        /     /       \                 \
       2     1         2                 3

1 class Solution {
     2 public:
     3     vector<TreeNode *> generateTrees(int n) {
     4         if (n == 0) return {};
     5         return *generateTreesDFS(1, n);
     6     }
     7     vector<TreeNode*> *generateTreesDFS(int start, int end) {
     8         vector<TreeNode*> *subTree = new vector<TreeNode*>();
     9         if (start > end) subTree->push_back(NULL);
    10         else {
    11             for (int i = start; i <= end; ++i) {
    12                 vector<TreeNode*> *leftSubTree = generateTreesDFS(start, i - 1);
    13                 vector<TreeNode*> *rightSubTree = generateTreesDFS(i + 1, end);
    14                 for (int j = 0; j < leftSubTree->size(); ++j) {
    15                     for (int k = 0; k < rightSubTree->size(); ++k) {
    16                         TreeNode *node = new TreeNode(i);
    17                         node->left = (*leftSubTree)[j];
    18                         node->right = (*rightSubTree)[k];
    19                         subTree->push_back(node);
    20                     }
    21                 }
    22             }
    23         }
    24         return subTree;
    25     }
    26 };

转载于:https://www.cnblogs.com/zzw1024/p/10817005.html