(attempt) 2.6

Author: Tony K Tan

lib/chapter2/2.6 - Palindrome/palindrome.js

@@ -0,0 +1,60 @@
+var LinkedList = require('./../util/LinkedList');
+
+var palindrome = function(head) {
+  var mid = head;
+  var end = head;
+  var isEven = true;
+  var firstHalf = null;
+  var frontNode = null;
+
+  while (end.next !== null) {
+    isEven = true;
+    if (firstHalf === null) {
+      firstHalf = new LinkedList(mid.value);
+    } else {
+      frontNode = firstHalf;
+      firstHalf = new LinkedList(mid.value);
+      firstHalf.next = frontNode;
+    }
+    mid = mid.next;
+    end = end.next;
+    if (end.next !== null) {
+      end = end.next;
+      isEven = false;
+    }
+  }
+
+  if (!isEven) {
+    mid = mid.next;
+  }
+
+  while(mid !== null) {
+    // console.log(mid.value, firstHalf.value);
+    if (mid.value !== firstHalf.value) {
+      return false;
+    }
+    mid = mid.next;
+    if (firstHalf!== null) {
+      firstHalf = firstHalf.next;
+    }
+  }
+  return true;
+
+};
+
+var a = new LinkedList('a');
+var b = new LinkedList('b');
+var c = new LinkedList('c');
+var d = new LinkedList('d');
+var e = new LinkedList('c');
+var f = new LinkedList('b');
+var g = new LinkedList('a');
+
+a.next = b;
+b.next = c;
+c.next = d;
+d.next = e;
+e.next = f;
+f.next = g;
+
+console.log(palindrome(a));