LeetCode in Kotlin
3503. Longest Palindrome After Substring Concatenation I
Medium
You are given two strings, s and t.
You can create a new string by selecting a substring from s (possibly empty) and a substring from t (possibly empty), then concatenating them in order.
Return the length of the longest palindrome that can be formed this way.
Example 1:
Input: s = “a”, t = “a”
Output: 2
Explanation:
Concatenating "a" from s and "a" from t results in "aa", which is a palindrome of length 2.
Example 2:
Input: s = “abc”, t = “def”
Output: 1
Explanation:
Since all characters are different, the longest palindrome is any single character, so the answer is 1.
Example 3:
Input: s = “b”, t = “aaaa”
Output: 4
Explanation:
Selecting “aaaa” from t is the longest palindrome, so the answer is 4.
Example 4:
Input: s = “abcde”, t = “ecdba”
Output: 5
Explanation:
Concatenating "abc" from s and "ba" from t results in "abcba", which is a palindrome of length 5.
Constraints:
1 <= s.length, t.length <= 30sandtconsist of lowercase English letters.
Solution
import kotlin.math.max
class Solution {
fun longestPalindrome(s: String, t: String): Int {
var maxLen = 0
maxLen = max(maxLen, longestPalindromicSubstring(s))
maxLen = max(maxLen, longestPalindromicSubstring(t))
val sLen = s.length
val tLen = t.length
for (i in 0..<sLen) {
for (j in i..<sLen) {
val m = j - i + 1
for (k in 0..<tLen) {
for (l in k..<tLen) {
val n = l - k + 1
val totalLength = m + n
if (totalLength <= maxLen) {
continue
}
var isPalindrome = true
for (p in 0..<totalLength / 2) {
val q = totalLength - 1 - p
val c1: Char = if (p < m) {
s[i + p]
} else {
t[k + (p - m)]
}
val c2: Char = if (q < m) {
s[i + q]
} else {
t[k + (q - m)]
}
if (c1 != c2) {
isPalindrome = false
break
}
}
if (isPalindrome) {
maxLen = totalLength
}
}
}
}
}
return maxLen
}
private fun longestPalindromicSubstring(str: String): Int {
var max = 0
val len = str.length
for (i in 0..<len) {
for (j in i..<len) {
var isPalin = true
var left = i
var right = j
while (left < right) {
if (str[left] != str[right]) {
isPalin = false
break
}
left++
right--
}
if (isPalin) {
max = max(max, (j - i + 1))
}
}
}
return max
}
}