108.convert-sorted-array-to-binary-search-tree.java

/*
 * @lc app=leetcode id=108 lang=java
 *
 * [108] Convert Sorted Array to Binary Search Tree
 */

// @lc code=start
/**
 * 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 sortedArrayToBST(int[] nums) {
        return sortedArrayToBST(nums, 0, nums.length - 1);
    }

    public TreeNode sortedArrayToBST(int[] nums, int left, int right) {
        if (left > right) {
            return null;
        }
        // 1 <= nums.length <= 10^4
        int mid = (left + right) / 2;
        TreeNode root = new TreeNode(nums[mid]);

        root.left = sortedArrayToBST(nums, left, mid - 1);
        root.right = sortedArrayToBST(nums, mid + 1, right);

        return root;
    }
}
// @lc code=end