[leedcode 108] Convert Sorted Array to Binary Search Tree

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    // ， ， start end， start end 
    // ， 
    public TreeNode sortedArrayToBST(int[] nums) {
        if(nums==null||nums.length==0) return null;
        return getBST(nums,0,nums.length-1);
    }
    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;
    }
}