[LintCode] Segment Tree Query

public int query(SegmentTreeNode root, int start, int end) {
        // write your code here
        if(root == null || root.start > end || root.end < start)
            return 0;
        if(root.start == root.end)
            return root.max;
        return Math.max(query(root.left,start,end),query(root.right,start,end));
    }