38 lines
782 B
Go
38 lines
782 B
Go
// Package q5 implements a solution for https://leetcode.com/problems/longest-palindromic-substring/
|
|
package q5
|
|
|
|
// Note: Although it can be done in O(N) with, e.g., Manacher's algorithm, the
|
|
// input size is small enough to brute-force.
|
|
|
|
func expand(s string, l, r int) (int, int) {
|
|
for l > 0 && r < len(s)-1 && s[l-1] == s[r+1] {
|
|
l--
|
|
r++
|
|
}
|
|
return l, r
|
|
}
|
|
|
|
func longestPalindrome(s string) string {
|
|
maxLen, mL, mR := 0, 0, 0
|
|
|
|
for c := range len(s) {
|
|
l, r := expand(s, c, c)
|
|
len_ := r - l + 1
|
|
if len_ > maxLen {
|
|
maxLen, mL, mR = len_, l, r
|
|
}
|
|
}
|
|
|
|
for c := range len(s) - 1 {
|
|
if s[c] == s[c+1] {
|
|
l, r := expand(s, c, c+1)
|
|
len_ := r - l + 1
|
|
if len_ > maxLen {
|
|
maxLen, mL, mR = len_, l, r
|
|
}
|
|
}
|
|
}
|
|
return s[mL : mR+1]
|
|
}
|
|
|
|
var _ = longestPalindrome
|