I had a problem where I was to find all he substrings of a string that are palindromes. Input would always be 1 word. The test input was aabaa. I decided to try be clever and make a string buffer of my substring then use the reverse method to compare with the original using String.equals. It didn't work.
import java.util.*
fun main(args: Array<String>) {
val scan = Scanner(System.`in`)
val input = scan.next()
val found = ArrayList<String>()
for (i in 0..input.length - 1) {
for (j in 0..input.length - i) {
val sub = input.substring(i, i + j)
if (!found.contains(sub)) {
// println(sub)
found.add(sub)
val rev = StringBuffer(sub).reverse()
if (sub.equals(rev)) {
println(rev)
}
}
}
}
}
When I uncomment the first print statement the output look like this using test input aabaa
a
aa
aab
aaba
aabaa
ab
aba
abaa
b
ba
baa
So I am getting the correct substrings, but the last if statement never resolves true and I don't know why this is.
sub
is a String. rev
is a StringBuffer. They can't be equal, since they don't even have the same type.
Additional notes:
for (i in 0..input.length - 1)
can be written for (i in 0 until input.length)
which is more elegant input.substring(i, i + j)
can't be right: at the end of the two loops, i would be length - 1, and j would be length - 1, and you would thus take a substring between length - 1 and 2 * length - 2. a == b
to test if a is equal to b, even if a and b are references.
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