From 8538210b738ffb49303f627e0bcde2dc9a1838fc Mon Sep 17 00:00:00 2001
From: Cameron Spickert <cspickert@google.com>
Date: Fri, 8 Jan 2016 11:15:07 -0500
Subject: [PATCH] Add Algorithms & Data Structures week 0 playground with code
 samples

---
 README.md                                     |  2 +
 .../Contents.swift                            | 93 +++++++++++++++++++
 .../contents.xcplayground                     |  4 +
 .../contents.xcworkspacedata                  |  7 ++
 .../timeline.xctimeline                       |  6 ++
 5 files changed, 112 insertions(+)
 create mode 100644 Unit4/unit-4_cameron_week-0.playground/Contents.swift
 create mode 100644 Unit4/unit-4_cameron_week-0.playground/contents.xcplayground
 create mode 100644 Unit4/unit-4_cameron_week-0.playground/playground.xcworkspace/contents.xcworkspacedata
 create mode 100644 Unit4/unit-4_cameron_week-0.playground/timeline.xctimeline

diff --git a/README.md b/README.md
index 24b2697..5c7a485 100644
--- a/README.md
+++ b/README.md
@@ -69,3 +69,5 @@ A wide variety of code samples taken directly from in-class lectures.
 [Stopwatch](https://github.com/accesscode-2-2/code-samples/tree/master/StopWatchDemo)  
 [Countdown](https://github.com/accesscode-2-2/code-samples/tree/master/TimerProject)
 
+**Algorithms & Data Structures**
+[Unit4](https://github.com/accesscode-2-2/code-samples/tree/master/Unit4)
diff --git a/Unit4/unit-4_cameron_week-0.playground/Contents.swift b/Unit4/unit-4_cameron_week-0.playground/Contents.swift
new file mode 100644
index 0000000..ba54b97
--- /dev/null
+++ b/Unit4/unit-4_cameron_week-0.playground/Contents.swift
@@ -0,0 +1,93 @@
+import UIKit
+
+// Linked Lists
+
+class ListNode {
+  var value: Int?
+  var next: ListNode?
+
+  init(value: Int, next: ListNode?) {
+    self.value = value
+    self.next = next
+  }
+
+  func removeHead() -> ListNode? {
+    let next = self.next
+    self.next = nil
+    return next
+  }
+}
+
+var head = ListNode(value: 5, next: ListNode(value: 6, next: ListNode(value: 7, next: nil)))
+
+let v = head.value
+head = head.removeHead()!
+
+head.value
+
+// Stacks
+
+struct Stack<Element> {
+  var array: [Element] = []
+
+  var isEmpty: Bool {
+    return array.isEmpty
+  }
+
+  func peek() -> Element? {
+    return array.last
+  }
+
+  mutating func push(element: Element) {
+    array.append(element)
+  }
+
+  mutating func pop() -> Element {
+    return array.removeLast()
+  }
+}
+
+func isBalanced(parens: String) -> Bool {
+  var s = Stack<Character>()
+  for c in parens.characters {
+    if c == "(" {
+      s.push(c)
+    } else if c == ")" {
+      if s.isEmpty {
+        return false
+      }
+      s.pop()
+    }
+  }
+  return s.isEmpty
+}
+
+isBalanced("(())()()(())(()()())()()")
+
+// Hash tables
+
+func hash(key: String) -> Int {
+  return key.characters.count - 1
+}
+hash("aa")
+hash("xy")
+
+"aa".hash
+"xy".hash
+
+// Graphs
+
+let graph: Dictionary<Int, [Int]> = [
+  0 : [4],
+  1 : [3, 4],
+  2 : [0, 1, 3],
+  3 : [4],
+  4 : []
+]
+
+let start = 2
+let connectedNodes = graph[start]
+let next = connectedNodes![0]
+let nextConnectedNodes = graph[next]
+
+// start.next....
diff --git a/Unit4/unit-4_cameron_week-0.playground/contents.xcplayground b/Unit4/unit-4_cameron_week-0.playground/contents.xcplayground
new file mode 100644
index 0000000..5da2641
--- /dev/null
+++ b/Unit4/unit-4_cameron_week-0.playground/contents.xcplayground
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>
\ No newline at end of file
diff --git a/Unit4/unit-4_cameron_week-0.playground/playground.xcworkspace/contents.xcworkspacedata b/Unit4/unit-4_cameron_week-0.playground/playground.xcworkspace/contents.xcworkspacedata
new file mode 100644
index 0000000..919434a
--- /dev/null
+++ b/Unit4/unit-4_cameron_week-0.playground/playground.xcworkspace/contents.xcworkspacedata
@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Workspace
+   version = "1.0">
+   <FileRef
+      location = "self:">
+   </FileRef>
+</Workspace>
diff --git a/Unit4/unit-4_cameron_week-0.playground/timeline.xctimeline b/Unit4/unit-4_cameron_week-0.playground/timeline.xctimeline
new file mode 100644
index 0000000..bf468af
--- /dev/null
+++ b/Unit4/unit-4_cameron_week-0.playground/timeline.xctimeline
@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<Timeline
+   version = "3.0">
+   <TimelineItems>
+   </TimelineItems>
+</Timeline>