[LeetCode 109］Convert Sorted List to Binary Search Tree

题目链接：convert-sorted-list-to-binary-search-tree

/** * Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST. * */public class ConvertSortedListToBinarySearchTree {public class ListNode {int val;ListNode next;ListNode(int x) {val = x;next = null;}}public class TreeNode {int val;TreeNode left;TreeNode right;TreeNode(int x) {val = x;}}//32 / 32 test cases passed.//Status: Accepted//Runtime: 294 ms//Submitted: 1 minute ago//自底向上法ListNode listHead;public TreeNode sortedListToBST(ListNode head) {this.listHead = head;ListNode cur = head;int len = 0;while(cur != null) {len++;cur = cur.next;}return sortedListToBST(0, len – 1);}public TreeNode sortedListToBST(int left, int right) {if(left > right) {return null;}int mid = (left + right) / 2;TreeNode leftNode = sortedListToBST(left, mid – 1);TreeNode root = new TreeNode(listHead.val);root.left = leftNode;listHead = listHead.next;root.right = sortedListToBST(mid + 1, right);return root;}public static void main(String[] args) {// TODO Auto-generated method stub}}

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