JadeNB,
In a nutshell, this problem boils down to where this number fits in a list. The obvious non-creative solution to this is a binary search because it is both space and time efficient.

It would also be fairly trivial if each chapter had the same number of sentences. One trick might be then to find the chapter with the most number of sentences and pad each chapter to be equal to that chapter. When you "hand out" sentences and their ordinal value, there will be gaps representing the padding but you can then instantly take any sentence and find which chapter it belongs to. You can also find its true overall ordinal value in the book as well as the ordinal value in the chapter. Consider the following: 

Chapter 1:  3 sentences
Chapter 2:  5 sentences
Chapter 3:  4 sentences
Chapter 4:  6 sentences

The chapter with the longest chapter is 4, so we pad all of them to 6

Chapter 1:  01, 02, 03             # 04, 05, 06 are padded
     real:  01, 02, 03
Chapter 2:  07, 08, 09, 10, 11     # 12 is padded
     real:  04, 05, 06, 07, 08
Chapter 3:  13, 14, 15, 16         # 17 and 18 are padded
     real:  09, 10, 11, 12
Chapter 4:  19, 20, 21, 22, 23, 24 # no padding
     real:  13, 14, 15, 16, 17, 18

Now let's say someone says, what chapter does 15 belong to?

ceil(15 / 6) = 3

Now let's say someone wants to know the true ordinal overall value

my %pad = (1 => 0, 2 => 3, 3 => 4, 4 => 6);

15 - $pad{ceil(15 / 6)} = 11

Now let's say someone wants to know what is the ordinal value of the s
+entence within the chapter

15 mod 6 = 3

[download]

Cheers - L~R

In reply to Re^3: chapters,sentences, and arrays by Limbic~Region
in thread chapters,sentences, and arrays by Anonymous Monk

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