After using comparator he is still subtracting 1

#1

I am not able to understand why he is subtracting 1 even after using comparator.
int lb=lower_bound(coins, coins+n, money, compare) - coins-1;
I am asking about this 1, which comparator gives element which is <=key then what is the need of doing this?

#2

hi… so we are using this -1 because consider the case of 120… over there we get ans as 200 while we need 100… we use compare comparator to handle cases like of 100

#3

But after reversing the comparison we should get 100.

#4

just try doing by removing -1… also dry run on some sample test… u would get better insight

#5

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