Husk, 14 bytes
§<ε#εu§m#u
m
<
Explanation
The two short lines are no-ops, since the main function never calls them.
§<ε#εu§m#u Implicit input, say S = "asasdd"
u Remove duplicates: "asd"
§m# For each, get number of occurrences in S: [2,2,2]
u Remove duplicates: L = [2]
#ε Number of elements in L that are at most 1: 0
ε 1 if L is a singleton, 0 otherwise: 1
§< Is the former value smaller than the latter?
Husk, 14 bytes
§<ε#εu§m#u
m
<
Explanation
The two short lines are no-ops, since the main function never calls them.
§<ε#εu§m#u Implicit input, say S = "asasdd"
u Remove duplicates: "asd"
§m# For each, get number of occurrences in S: [2,2,2]
u Remove duplicates: L = [2]
#ε Number of elements in L that are at most 1: 0
ε 1 if L is a singleton, 0 otherwise: 1
§< Is the former value smaller than the latter?