Uncaught TypeError: $(...).autocomplete is not a function

Uncaught TypeError: $(...).autocomplete is not a function

Hi I am working on ASP.NET project and i want to use autocomplete feature of jquery. Every time it gives same error " Uncaught TypeError: $(...).autocomplete is not a function " i tried hard but i could not fix my problem. I googled lot still facing same problem. Kindly help me
Here is my code :

  <script src="jquery/jquery-1.10.2.js" type="text/javascript"></script>
    <link rel="stylesheet" href="//code.jquery.com/ui/1.11.2/themes/smoothness/jquery-ui.css"/>
   <script src="//code.jquery.com/ui/1.11.2/jquery-ui.js"> </script>
    <script type="text/javascript">
        $(function () {
            $('#<%=txt_SearchCity.ClientID%>').autocomplete({
                source: function (request, response) {
                    $.ajax({
                        url: "WebService_AutoComplete.asmx/GetAutoCompleteData",
                        data: "{'searchTerm':'" + request.term + "'}",
                        type: "POST",
                        dataType: "json",
                        contentType: "application/json;charset=utf-8",
                        success: function (data) {
                            response(data.d);
                        },
                        error: function (result) {
                            alert("there is a problem in processing request");
                        }

                    })
                }
            })
        });
    </script>