public TreeNode constructMaximumBinaryTree(int[] nums) {

        if (nums.length==0) return null;

        return builder(nums,0,nums.length-1);

    }

    public TreeNode builder(int[] nums,int sta,int end)

    {

        /*

        思路就是每次找到最大值，然后分为两个子数组递归构建左右树

         */

        if (sta>end) return null;

        int max = Integer.MIN_VALUE;

        int index = -1;

        for (int i = sta; i <= end ; i++) {

            if (nums[i]>max)

            {

                max = nums[i];

                index = i;

            }

        }

        TreeNode root = new TreeNode(max);

        root.left = builder(nums,sta,index-1);

        root.right = builder(nums,index+1,end);

        return root;

    }