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109.有序链表转换二叉搜索树.js
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109.有序链表转换二叉搜索树.js
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/*
* @lc app=leetcode.cn id=109 lang=javascript
*
* [109] 有序链表转换二叉搜索树
*/
// @lc code=start
/**
* Definition for singly-linked list.
* function ListNode(val, next) {
* this.val = (val===undefined ? 0 : val)
* this.next = (next===undefined ? null : next)
* }
*/
/**
* Definition for a binary tree node.
* function TreeNode(val, left, right) {
* this.val = (val===undefined ? 0 : val)
* this.left = (left===undefined ? null : left)
* this.right = (right===undefined ? null : right)
* }
*/
/**
* @param {ListNode} head
* @return {TreeNode}
*/
var sortedListToBST = function(head) {
// Converting LL into array
let arr = getarr(head);
// Now, using tree function to get an tree out of SORTED ARRAY
return tree(arr);
};
function getarr(head){
if(!head) return [];
let temp = head;
let out = []
while(temp){
out.push(temp.val);
temp = temp.next;
}
return out;
}
function tree(nums, start=0, end = nums.length-1) {
if(start<=end){
let mid = Math.floor((start+end)/2);
// console.log(mid, end)
let root = new TreeNode(nums[mid]);
root.left = tree(nums, start, mid-1);
root.right = tree(nums, mid+1, end);
return root;
}
return null;
};
// @lc code=end