fix(2.2): redo returnKthToLast (careercup#67)

Author: charitymarani

chapter02/2.2 - Return Kth to Last/returnKthToLast.js

@@ -1,42 +1,41 @@
-var linkedList = function(value) {
-  this.value = value;
-  this.next = null;
-};
+const LinkedList = require("../util/LinkedListX");
+
+var findKthToLast = function(k, list) {
+  // do iteratively
+  //define two pointers , fast and slow pointer
+  let fast = list.head
+  let slow = list.head
+
+  //Move fast pointer k steps in the linkedlist while slow remains at head
+  for(let i=0;i<k;i++){
+    if(fast === null) return null //k is larger than length of linked list
+    fast = fast.next
+  }
+  // move both pointers at the same time, slow pointer will exit at kth node from the end
+  while(fast !== null){
+    fast =fast.next
+    slow=slow.next
 
-var findKthToLast = function(k, head) {
-  // do recursively
-  if (head === null || k < 1) {
-    return;
-  } else if (k === 1) {
-    console.log(head.value);
-    findKthToLast(k, head.next);
-  } else {
-    findKthToLast(k-1, head.next);
   }
-};
+  return slow
 
+};
 /* TESTS */
-var a = new linkedList('1');
-var b = new linkedList('2');
-var c = new linkedList('3');
-var d = new linkedList('4');
-var e = new linkedList('5');
-var f = new linkedList('6');
-var g = new linkedList('7');
+let l = new LinkedList();
+l.append(1)
+l.append(2)
+l.append(3)
+l.append(4)
+l.append(5)
+
 
-a.next = b;
-b.next = c;
-c.next = d;
-d.next = e;
-e.next = f;
-f.next = g;
 
-findKthToLast(3, a);
+console.log(findKthToLast(3, l));
 
-findKthToLast(10, a);
+console.log(findKthToLast(10, l));
 
-findKthToLast(-1, a);
+console.log(findKthToLast(-1, l));
 
-findKthToLast(0, a);
+console.log(findKthToLast(0, l));
 
-findKthToLast(1, a);
+console.log(findKthToLast(1, l));

chapter02/2.3 - Delete Middle Node/deleteMiddleNode.js

@@ -1,48 +1,21 @@
-var LinkedList = function(value) {
-  this.value = value;
-  this.next = null;
-};
+const LinkedList = require("../util/LinkedListX");
+const printList = require("../util/printList");
+
+let deleteMidNode = function(node) {
 
-var deleteMidNode = function(midNode) {
-  var node = midNode;
-  while (node !== null && node.next !== null) {
+  if(node !== null && node.next !== null) {
     node.value = node.next.value;
-    if (node.next.next === null) {
-      node.next = null;
-    } 
-    node = node.next;
-  }
+    node.next = node.next.next;
+    }
 };
 
-// a -> b -> c -> d -> e -> f, input c
-// a -> b -> *d -> d -> e -> f
-// a -> b -> d -> *e -> e -> f
-// a -> b -> d -> e -> *f -> f
-// a -> b -> d -> e -> f -> *null
-
 /* TEST */
 
-var printList = function(head) {
-  while(head !== null) {
-    console.log(head.value);
-    head = head.next;
-  }
-  console.log('done printing');
-};
-
-var a = new LinkedList('a');
-var b = new LinkedList('b');
-var c = new LinkedList('c');
-var d = new LinkedList('d');
-var e = new LinkedList('e');
-var f = new LinkedList('f');
-
-a.next = b;
-b.next = c;
-c.next = d;
-d.next = e;
-e.next = f;
+let list = new LinkedList();
+for (let item of [1, 2, 3, 4, 5, 6]) {
+  list.append(item);
+}
 
-printList(a);
-deleteMidNode(c);
-printList(a);
+printList(list.head);
+deleteMidNode(list.head.next);
+printList(list.head);