The data is sorted lexicographically on the first number.

You mean like this?

C:\Users\HomeAdmin>perl -E"@s = 1..30; say for sort @s"
1
10
11
12
13
14
15
16
17
18
19
2
20
21
22
23
24
25
26
27
28
29
3
30
4
5
6
7
8
9

[download]

Also, what are the smallest and largest keys ("first numbers") in the file?

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'
Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority". I'm with torvalds on this
In the absence of evidence, opinion is indistinguishable from prejudice. Agile (and TDD) debunked

In reply to Re^3: Using indexing for faster lookup in large file by BrowserUk
in thread Using indexing for faster lookup in large file by anli_

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