Given a string s, s to find the longest substring palindromic. You can assume that the maximum length of 1000 s.
Example 1:
Enter: "babad" Output: "bab" Note: "aba" is a valid answer.
Example 2:
Enter: "cbbd" Output: "bb"
Center expansion method
Code:
package main
import (
"math"
"fmt"
)
func main() {
var str = "cbbd"
var palindrome = longestPalindrome(str)
fmt.Println(palindrome)
}
func longestPalindrome(s string) string {
arr := []byte(s)
length := len(arr)
if length == 0 || length == 1 {
return s
}
var start, end, mlen = 0, 0, 0
for i := 0; i < length; i ++ {
len_1 := expendaroundcenter(s, i, i)
len_2 := expendaroundcenter(s, i, i+1)
mlen = int(math.Max(float64(len_1), float64(len_2)))
if mlen > end - start + 1 {
start = i - (mlen - 1)/2
end = i + mlen/2
}
}
return string(arr[start:end+1])
}
func expendaroundcenter(s string, left int, right int) int{
arr := []byte(s)
l := left
r := right
for {
//fmt.Printf("r:%d l:%d \n", r, l)
if l >= 0 && r < len(arr) && arr[l] == arr[r] {
l --
r ++
} else {
break
}
}
return r - l - 1
}