Longest Palindromic Substring

Find the longest palindromic substring from a long string.

1. Iterate from i := 1 to i := n-1 considering i^th value as the center of Palindromic substring.
2. Iterating from the ith value towards left and right, look for an even length palindromic substring.
   Eg: abcddcaa
   Longest palindromic substring is : cddc
3. Iterating from the ith value towards left and right, look for an even length palindromic substring.
   Eg: xyxabcdcba
   Longest palindromic substring is : abcdcba
4. After identifying each palindrome string, compare with previously identified value and replace.

package main
import "fmt"
func main() {
 str := "abcxxyyxxdef"
 palindrome := ""
 for i := 1; i < len(str)-1; i++ {
  if tmpPalindrome := getPalindromicSubstr(str, i, true); tmpPalindrome != "" && len(tmpPalindrome) > len(palindrome) {
   palindrome = tmpPalindrome
  }
  if tmpPalindrome := getPalindromicSubstr(str, i, false); tmpPalindrome != "" && len(tmpPalindrome) > len(palindrome) {
   palindrome = tmpPalindrome
  }
 }
  if palindrome == ""{
    palindrome = str[:1]
  }
 fmt.Println("Longest palindromic substring : ", palindrome)
}
func getPalindromicSubstr(str string, idx int, odd bool) string {
 lenStr := len(str)
 palindrome := ""
var i, j int
 if odd {
  i = idx - 1
  j = idx + 1
 } else {
  i = idx - 1
  j = idx
 }
for i >= 0 && j < lenStr {
  if tmp, ok := isPalindrome(str, i, j); ok {
   palindrome = tmp
   i--
   j++
  } else {
   return palindrome
  }
 }
return palindrome
}
func isPalindrome(str string, idxStart, idxEnd int) (string, bool) {
 subStr := str[idxStart : idxEnd+1]
 lastIdx := len(subStr) - 1
 for i := 0; i < lastIdx/2 && i < (lastIdx-i); i++ {
  if subStr[i] != subStr[lastIdx-i] {
   return "", false
  }
 }
 return subStr, true
}

Time Complexity : O(n2)
Space Complexity : O(1)