70. Climbing Stairs

问题
You are climbing a staircase. It takes n steps to reach the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

递归,传入根节点,进行BFS搜索。
如果当前节点小于搜索的最低点,则抛弃该节点,继续搜索其右子节点。(由于是BST,右子节点大于节点本身)
如果当前节点大于搜索的最高点,则抛弃该节点,继续搜索其左子节点。
如果当前节点在搜索范围内,则保留该节点,继续递归该节点的两个子节点。
最后返回根节点。

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/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public TreeNode trimBST(TreeNode root, int low, int high) {
if(root == null){
return null;
}
if(root.val < low){
return trimBST(root.right, low, high);
}
if(root.val > high){
return trimBST(root.left, low, high);
}

root.left = trimBST(root.left, low, high);
root.right = trimBST(root.right, low, high);
return root;
}
}
Author

Xander

Posted on

2022-04-15

Updated on

2022-04-14

Licensed under

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