From e82c08f9afef904a946eadb72f83bf6a5c7c44c6 Mon Sep 17 00:00:00 2001
From: krlv <eug.krlv@gmail.com>
Date: Thu, 14 Mar 2019 19:01:34 -0700
Subject: [PATCH] Q2.6: Palindrome: iterative implementation improvement

---
 ch02/06_palindrome.go      | 18 +++++++++++-------
 ch02/06_palindrome_test.go |  4 ++--
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/ch02/06_palindrome.go b/ch02/06_palindrome.go
index 0a3bc89..1d19eaf 100644
--- a/ch02/06_palindrome.go
+++ b/ch02/06_palindrome.go
@@ -27,21 +27,25 @@ func IsPalindrome(node *Node) bool {
 	return true
 }
 
-// IsPalindromeList checks if the linked list is a palindrome
+// IsPalindromeIterative checks if the linked list is a palindrome
 // Implementation is based on Node.Len() method
 // and uses a list as a storage for reverse values
-func IsPalindromeList(node *Node) bool {
+func IsPalindromeIterative(node *Node) bool {
 	nlen := node.Len()
-	revl := make([]int, nlen)
+	xlen := nlen / 2
+	revl := make([]int, xlen)
 
 	tail := node
-	for i := 0; i < nlen; i++ {
-		revl[nlen-1-i] = tail.data
+	for i := 0; i < xlen; i++ {
+		revl[xlen-1-i] = tail.data
 		tail = tail.next
 	}
 
-	tail = node
-	for i := 0; i < nlen; i++ {
+	if nlen%2 == 1 {
+		tail = tail.next
+	}
+
+	for i := 0; i < xlen; i++ {
 		if revl[i] != tail.data {
 			return false
 		}
diff --git a/ch02/06_palindrome_test.go b/ch02/06_palindrome_test.go
index e3e4e71..e443880 100644
--- a/ch02/06_palindrome_test.go
+++ b/ch02/06_palindrome_test.go
@@ -38,7 +38,7 @@ func TestIsPalindromeList(t *testing.T) {
 	node.AppendToTail(3)
 	node.AppendToTail(4)
 
-	if IsPalindromeList(node) {
+	if IsPalindromeIterative(node) {
 		t.Error("Expected the linked list to be not a palindrome")
 	}
 
@@ -57,7 +57,7 @@ func TestIsPalindromeList(t *testing.T) {
 	node.AppendToTail(2)
 	node.AppendToTail(1)
 
-	if !IsPalindromeList(node) {
+	if !IsPalindromeIterative(node) {
 		t.Error("Expected the linked list to be a palindrome")
 	}
 }