Excel - find the biggest gap between numbers in rows - excel

Question

I have an excel file with >12500 rows in one column.
It contains such random strings with 20 digits:
2,3,4,6,7,8,12,13,14,24,30,42,45,46,48,50,56,58,**59**,61
1,2,6,8,11,12,13,16,17,21,24,27,28,33,34,42,44,48,58,61
3,7,10,13,14,15,18,21,23,24,25,29,30,34,37,48,51,56,57,60
8,11,13,16,17,19,21,27,29,35,36,39,42,44,46,50,53,54,57,60
2,4,7,9,21,26,28,30,32,34,35,37,38,39,43,44,50,60,61,62
10,13,15,18,21,22,23,24,25,26,40,42,48,49,51,52,56,**59**,61,62
1,2,4,7,14,15,18,20,24,29,30,32,35,41,42,50,52,55,58,62
1,4,8,9,10,12,17,24,25,33,37,41,43,44,46,49,52,**59**,61,62
1,2,4,6,9,12,15,17,21,24,30,31,32,36,41,44,47,48,51,58
2,7,10,12,15,16,20,24,25,27,30,33,39,44,45,52,54,55,58,60
5,7,10,11,20,22,24,31,32,33,36,38,39,41,43,47,50,52,56,58
3,6,8,9,14,15,19,21,25,28,34,37,39,45,47,54,55,56,57,**59**
1,2,3,4,5,8,14,15,18,20,23,31,33,37,42,45,46,51,52,55
I need to know whats the biggest gap between rows where a number hasn't repeated. For example - I search for any number (e.g 59) and I need to know what's the largest gap between two rows where number 59 hasn't repeated.
In this example it's 4 row gap between 59's.
Hope that I make myself clear.

Answer 1

Seems like a fun problem which admits a simple but not quite obvious answer. First -- make sure that the data is in 20 columns (use the text to columns feature under the data tab). Using your example, I came up with a spreadsheet that looks like:
V1 holds the target number. The formulas are in columns U.
In U1 I entered:
=IF(ISNA(MATCH($V$1,A1:T1,0)),1,0)
This formula uses MATCH to test if the value in V1 lies in the range to the left of it. If it doesn't the match function returns #N/A. The function ISNA checks for this error value. IF it is present, the overall formula returns 1 (since there are now 1 consecutive row without the target number) otherwise it returns 0.
The formula in U2 is similar with a little twist:
=IF(ISNA(MATCH($V$1,A2:T2,0)),1+U1,0)
The same basic logic -- but rather than returning 1 if the target number isn't present it adds 1 to the number above. The formula is then copied down the rest of the range. It has the effect of keeping a running total of consecutive rows without the target value. This running total is reset to 0 whenever a row with the target value is encountered.
The final ingredient requires no comment. In U14 I just have
=MAX(U1:U13)
which is the number you are looking for (assuming that the maximum number of consecutive rows without the target number is what you are looking for, even if this occurs either at the top or bottom of the data. If you want the largest gap that is literally between two rows where the number occurs, the logic would need to be made more complex).