longest palindrome

pals.go

package main

import ( 
	"fmt"
	"io/ioutil"
)

// " \t\r\n"
var spaces = map[byte]bool{ 32: true, 9: true, 10: true, 13: true }


func longestPalindrome(text []byte) ([]byte, int, int) {

	textlen := len(text)
	maxlen  := 0
	maxlow  := 0
	maxhigh := 0
	low     := 0
	high    := 0

	var current byte 
	var previous byte

	for i := range text { 

		// lowercase char
		if text[i] > 64 && text[i] < 91 { text[i] += 32 }

		// Handle both odd and even-length palindromes
		for j := i; j < i + 2 && j < textlen; j ++ {

			low  = i
			high = j

			// Expand while the subregion is a valid palindrome
			for text[low] == text[high] { 

				// discount multiple spaces
				current = text[low]
				if spaces[current] && spaces[previous] { break }

				// If longest found, update
				if high - low > maxlen { 
					maxlow  = low
					maxhigh = high
					maxlen  = maxhigh - maxlow
				}

				// update prev
				previous = current

				// expand indexes
				if low > 0 { low  -- } else { break }
				if high < textlen - 1 { high ++ } else { break }
			}
		}
	} 

	maxhigh ++; if maxhigh > textlen { maxhigh = textlen }

	return text[maxlow : maxhigh], maxlow, maxhigh
}


func main() {

	text, _ := ioutil.ReadFile("war_and_peace.txt")

	str, _, _ := longestPalindrome(text)
	
	fmt.Println(string(str))
	fmt.Println(str)
}