题目: 在二叉查找树中插入节点
要求:
给定一棵二叉查找树和一个新的树节点,将节点插入到树中。
你需要保证该树仍然是一棵二叉查找树。
样例:
给出如下一棵二叉查找树,在插入节点6之后这棵二叉查找树可以是这样的:
给出如下一棵二叉查找树,在插入节点6之后这棵二叉查找树可以是这样的:
2 2
/ \ / \
1 4 --> 1 4
/ / \
3 3 6
算法要求:
能否不使用递归?
解题思路:
直接用栈来实现即可。
算法如下:
/**
* Definition of TreeNode:
* class TreeNode {
* public:
* int val;
* TreeNode *left, *right;
* TreeNode(int val) {
* this->val = val;
* this->left = this->right = NULL;
* }
* }
*/
class Solution {
public:
/*
* @param root: The root of the binary search tree.
* @param node: insert this node into the binary search tree
* @return: The root of the new binary search tree.
*/
TreeNode * insertNode(TreeNode * root, TreeNode * node) {
// write your code here
stack<TreeNode * > sta;
sta.push(root);
TreeNode * last = NULL;
while (sta.size() != 0) {
TreeNode * now = sta.top();
sta.pop();
if (now == NULL) {
if (last == NULL) {
root = node;
} else if (last->val <= node->val) {
last -> right = node;
} else {
last -> left = node;
}
break;
} else if (now->val <= node->val) {
sta.push(now->right);
} else {
sta.push(now->left);
}
last = now;
}
return root;
}
};