i don’t understand how > for (auto Letter : Word) can loop through letters and how > if (LetterSeen[Letter]) can compare the letters
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for (auto Letter : Word)
this essentially means “for each Letter in the Word”
auto just lets the program automatically determine that Letter is a char, rather than you having to write char yourself
if (LetterSeen[Letter])
LetterSeen is a lookup table, so if Letter is 'A' it looks to see if LetterSeen table already has an entry for A. If so then you’ve got a duplicate
eg for AMBULANCE, LetterSeen['A'] is set true for the first character, and then when you get to the sixth character, LetterSeen['A'] will already be true, hence you have a duplicate letter A, and can exit the loop, reporting that it is not an ISOGRAM
LetterSeen TMAP
==========================
Letter | Seen
--------------------------
A | True <= Already True, so can't have another 'A'
B | True
C | True
D |
E |
F |
G |
...
...
L | True
M | True
N | True
etc
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