How to generate 10 digit unique number.

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I want to generate 10 digit unique number, i have tried with date and time but it goes arround 14 digit. so please tell me how can i generate 10 digit unique number. Even if i restart the application it should maintain the uniqueness in the new generated number.
I can able to generate the 14 digit unique number. Is possible to scale down this 14 digit number into 10 digit unique number ?

Posted 18-May-11 2:18am

LaxmikantYadav

Updated 18-May-11 22:56pm

v3

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Comments

Niklas L 18-May-11 8:24am

Your question makes no sense. Unique compared to what? Start with 1000000000 and add 1 each time. That will give you all possible ten digit unique numbers. (A 32 bit representation is not enough, so pick a 64 bit integer.)

LaxmikantYadav 18-May-11 8:51am

In this solution i have stored last number. And after generation of new number again have to update the last stored number which is not fixible. I want to generate number like using datetime but i want it upto 10 digit.

వేంకటనారాయణ(venkatmakam) 18-May-11 9:25am

I think Niklas Lindquist given a easy solution. you will have only one 10 digit number and whenever you want to generate a number just increment it as uniqueNumber++;There is no need of updating last number.

LaxmikantYadav 18-May-11 9:43am

Suppose i generate 10 number using niklas's logic and exit from application then on next run how can i generate unique number without storing previous unique number.

వేంకటనారాయణ(venkatmakam) 18-May-11 10:00am

this is the real requirement. This has to be mentioned in your question.So the requirement is that you have to generate a 10 digit unique number,Like a roll number for a student,right.

LaxmikantYadav 19-May-11 0:12am

Yes, can you help me in this ?

CPallini 19-May-11 5:57am

Why cannot you store last unique number?

LaxmikantYadav 26-May-11 0:38am

If i stored the last unique number then i have to maintain it and it is difficult to maintain this number while crashing the application.

5 solutions

Solution 1

Look at the below link. This may help you
http://forums.asp.net/t/1170804.aspx[^]

Kiran

Posted 18-May-11 2:31am

Kiran Sonawane

Comments

LaxmikantYadav 18-May-11 8:47am

Guid is so long in size, I want upto 10 digit long.

Solution 4

Use unix time format:
http://uk.answers.yahoo.com/question/index?qid=20090928054656AAis0fq[^]

Posted 18-May-11 4:10am

uToLs

Comments

Sergey Alexandrovich Kryukov 18-May-11 15:45pm

This is good, but only if request stay apart in couple of milliseconds or so.
--SA

Solution 5

I don't think using a combination of date and time is the right one, since the smallest unit you can get is millisecond.

I would go with GUID. But if you insist that it has to be done with time, than I think a combination of GetTickCount[^] (beware of its 49.7 days limitation or better GetTickCount64[^]) and a rand()[^] would be sufficient.

Posted 18-May-11 6:24am

Stephen Wiria

Comments

Sergey Alexandrovich Kryukov 18-May-11 15:45pm

GUID is not 100% guarantee.
--SA

Stephen Wiria 18-May-11 19:11pm

True, I believe unique here means practically unique.
But then again, I don't think he could get a better and easier solution than GUID

LaxmikantYadav 19-May-11 0:17am

GUID is greater than 10 digit. and if i use GetTickCount it is fine for first time. once i restart the pc it will again give me the same number. so uniqueness of the numbers can not be maintain.

Stephen Wiria 19-May-11 1:51am

Yes, GetTickCount gives system uptime in milliseconds.
Right now, I can't give you better solution other than GUID. Sorry.

Solution 2

VB.NET
Dim RandomNumber As Integer
RandomNumber = RandomClass.Next(999999999,9999999999)

Posted 18-May-11 2:50am

JustWorking

Comments

LaxmikantYadav 18-May-11 8:52am

I want in C++, And in this way we cant maintain the uniqueness of numbers.

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tolw · Accepted Answer · 2011-05-18T23:20:00

Solution 6

This might help a little: Link[^]

The post describes the GUID generation algorithm and how it can be modified for specific situations to be shorter. Interesting read.

Posted 18-May-11 23:20pm

tolw

Comments

fjdiewornncalwe 19-May-11 10:47am

It is indeed an interesting read. Great find. +5

LaxmikantYadav 26-May-11 0:39am

Guid is so long, I want upto 10 digit long.

tolw 26-May-11 3:51am

That's why i suggested READING the article I linked to and NOT using GUID. At the end of the article there is a real live example of how to create your own guid-like id which can be shorter then the real guid, but has some specific limitations.

How to generate 10 digit unique number.

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