108.java

class Problem108 {
    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;
        }
    }
    public TreeNode sortedArrayToBST(int[] nums) {
        return getBST(nums, 0, nums.length-1);
    }
    public TreeNode getBST(int[]nums, int start, int end){
        if (start > end)
            return null;
        int mid = (start+end)/2;
        TreeNode node = new TreeNode(nums[mid]);
        node.left = getBST(nums, start, mid-1);
        node.right = getBST(nums, mid+1, end);
        return node;
    }
}