701-二叉搜索树中的插入操作

LeetCode 701. Insert into a Binary Search Tree

LeetCode-701

You are given the root node of a binary search tree (BST) and a value to insert into the tree. Return the root node of the BST after the insertion. It is guaranteed that the new value does not exist in the original BST.

Notice that there may exist multiple valid ways for the insertion, as long as the tree remains a BST after insertion. You can return any of them.

Example 1:

Input: root = [4,2,7,1,3], val = 5
Output: [4,2,7,1,3,5]

method

按照二叉搜索树的规则进行遍历，遇到空节点就是需要插入的位置，新建并返回该节点

TreeNode* insertIntoBST(TreeNode* root, int val) {
    if (!root) {
        TreeNode *node = new TreeNode(val);
        return node;
    }
    if (val < root->val) root->left = insertIntoBST(root->left, val);
    else root->right = insertIntoBST(root->right, val);
    return root;
}