diff --git a/MoreSwiftBasics.playground/Pages/Arrays.xcplaygroundpage/Contents.swift b/MoreSwiftBasics.playground/Pages/Arrays.xcplaygroundpage/Contents.swift
index c398900..af7ab62 100644
--- a/MoreSwiftBasics.playground/Pages/Arrays.xcplaygroundpage/Contents.swift
+++ b/MoreSwiftBasics.playground/Pages/Arrays.xcplaygroundpage/Contents.swift
@@ -125,24 +125,33 @@ var animalArray: [String] = ["Lion", "Zebra", "Elephant", "Turtle"]
 var optionalArray: [Int]?
 
 // [2] Is there a logical error with accessing index `4` in a 4-element array?
-print("4th element of animalArray: \(animalArray[4])")
+print("4th element of animalArray: \(animalArray[3])")
 
 // [3] The operation below is quite dangerous. How can we make it safer?
-let unwrappedArray = optionalArray!
-print(unwrappedArray)
+if let unwrappedArray = optionalArray {
+    print(unwrappedArray)
+} else {
+    print("optionalArray is nil")
+}
 
 
 // [4] Initialize optionalArray
 /* BEGIN CODE */
-
+optionalArray = []
 /* END CODE */
 
 // [5, 6, 7] Add elements to optionalArray
 /* BEGIN CODE */
-
+optionalArray?.append(10)
+optionalArray?.append(contentsOf: [6, 7, 8, 9])
+optionalArray?.insert(55, at: 2)
 /* END CODE */
 
 // [8] Print the 5th element of optionalArray
 /* BEGIN CODE */
-
+if let optionalArray = optionalArray, optionalArray.count >= 5 {
+    print("5th element of optionalArray: \(optionalArray[4])")
+} else {
+    print("optionalArray doesn't have a 5th element")
+}
 /* END CODE */
diff --git a/MoreSwiftBasics.playground/Pages/FunctionsClosures.xcplaygroundpage/Contents.swift b/MoreSwiftBasics.playground/Pages/FunctionsClosures.xcplaygroundpage/Contents.swift
index ef9424a..e10f057 100644
--- a/MoreSwiftBasics.playground/Pages/FunctionsClosures.xcplaygroundpage/Contents.swift
+++ b/MoreSwiftBasics.playground/Pages/FunctionsClosures.xcplaygroundpage/Contents.swift
@@ -242,7 +242,7 @@ print("Alphabetical:   \(cities)\n")
 // [1] Use the .sort(by:) function to sort the array from shortest name to
 //     longest. Check the docs for reference material if needed
 /* BEGIN CODE */
-
+cities.sort(by: { $0.count < $1.count })
 /* END CODE */
 print("Length (.sort): \(cities)")
 
@@ -264,10 +264,21 @@ for i in 0 to (arr_length - 1):
 */
 func selectionSort(_ input: [String]) -> [String] {
     var arr: [String] = input
-    /* BEGIN CODE */
-    
-    /* END CODE */
+    for i in 0..<arr.count {
+        var minIndex = i
+        for j in (i + 1)..<arr.count {
+            if arr[j].count < arr[minIndex].count {
+                minIndex = j
+            }
+        }
+        if i != minIndex {
+            let temp = arr[i]
+            arr[i] = arr[minIndex]
+            arr[minIndex] = temp
+        }
+    }
     return arr
 }
+
 cities2 = selectionSort(cities2)
 print("Length (sel):   \(cities2)")
diff --git a/MoreSwiftBasics.playground/Pages/Loops.xcplaygroundpage/Contents.swift b/MoreSwiftBasics.playground/Pages/Loops.xcplaygroundpage/Contents.swift
index 8d9b3a8..a359a73 100644
--- a/MoreSwiftBasics.playground/Pages/Loops.xcplaygroundpage/Contents.swift
+++ b/MoreSwiftBasics.playground/Pages/Loops.xcplaygroundpage/Contents.swift
@@ -137,11 +137,9 @@ var numArr: [Int] = Array(repeating: 0, count: 5)
 
 // [1] Rewrite this code to use a loop
 /* BEGIN CODE */
-numArr[0] = 10
-numArr[1] = 20
-numArr[2] = 30
-numArr[3] = 40
-numArr[4] = 50
+for i in 0..<numArr.count {
+    numArr[i] = (i + 1) * 10
+}
 /* END CODE */
 print("numArr: \(numArr)")
 // <-- [RUN HERE] The output should be unchanged
@@ -161,7 +159,9 @@ var messages: [String: String] = [
 //     Reference the docs for the desired output format.
 print("\nMessage Data:")
 /* BEGIN CODE */
-
+for (id, message) in messages {
+    print("\(id): \(message)")
+}
 /* END CODE */
 // <-- [RUN HERE] Does this seem like the order of a normal conversation?
 //                Perhaps we're missing some data about which messages
@@ -184,27 +184,50 @@ print("Goodbye!")
 //     Refer to the docs for tips & tricks.
 print("\n(WHILE) MESSAGES: ")
 /* BEGIN CODE */
-
+var index = 0
+while index < messageOrder.count {
+    let id = messageOrder[index]
+    if let message = messages[id] {
+        print(message)
+    }
+    index += 1
+}
 /* END CODE */
 // <-- [RUN HERE] Check if your output matches the example.
 
 // [4] Do the same thing, but with a repeat-while loop
 print("\n(REPEAT-WHILE) MESSAGES: ")
 /* BEGIN CODE */
-
+index = 0
+repeat {
+    let id = messageOrder[index]
+    if let message = messages[id] {
+        print(message)
+    }
+    index += 1
+} while index < messageOrder.count
 /* END CODE */
 // <-- [RUN HERE] Check if your output matches the example.
 
 // [5] Do the same thing, but with a for loop using default iterator
 print("\n(FOR ITERATOR) MESSAGES: ")
 /* BEGIN CODE */
-
+for id in messageOrder {
+    if let message = messages[id] {
+        print(message)
+    }
+}
 /* END CODE */
 // <-- [RUN HERE] Check if your output matches the example.
 
 // [6] Do the same thing, but with a for loop using a range
 print("\n(FOR RANGE) MESSAGES: ")
 /* BEGIN CODE */
-
+for i in 0..<messageOrder.count {
+    let id = messageOrder[i]
+    if let message = messages[id] {
+        print(message)
+    }
+}
 /* END CODE */
 // <-- [RUN HERE] Check if your output matches the example.
diff --git a/MoreSwiftBasics.playground/Pages/SetsDictionaries.xcplaygroundpage/Contents.swift b/MoreSwiftBasics.playground/Pages/SetsDictionaries.xcplaygroundpage/Contents.swift
index 0c6534e..a62ea1a 100644
--- a/MoreSwiftBasics.playground/Pages/SetsDictionaries.xcplaygroundpage/Contents.swift
+++ b/MoreSwiftBasics.playground/Pages/SetsDictionaries.xcplaygroundpage/Contents.swift
@@ -144,34 +144,50 @@ if !mySet.contains("Zebra") {
 
 // [2] Declare an optional String-Set, but don't initialize it
 /* BEGIN CODE */
-
+var mySet: Set<String> = ["Zebra"]
+if !mySet.contains("Zebra") {
+    print("--> FAILURE: mySet does not contain Zebra")
+} else if !mySet.isSubset(of: animalSet) {
+    print("--> FAILURE: mySet is not a subset of animalSet")
+} else {
+    print("SUCCESS: mySet contains Zebra and is a subset of animalSet")
+}
 /* END CODE */
-
+var optionalSet: Set<String>?
 // [3] Insert "Giraffe" into optionalSet.
 /* BEGIN CODE */
-
+optionalSet?.insert("Giraffe")
 /* END CODE */
 
 // [4] Check if optionalSet contains "Giraffe"
 /* BEGIN CODE */
-
+if let set = optionalSet, set.contains("Giraffe") {
+    print("optionalSet contains Giraffe")
+} else {
+    print("optionalSet does not contain Giraffe")
+}
 /* END CODE */
 // <-- [RUN HERE] optionalSet should NOT contain Giraffe at this point
 
 // [5] Initialize optionalSet with "Cow", "Elephant"
 // (can be done in one line)
 /* BEGIN CODE */
-
+optionalSet = ["Cow", "Elephant"]
 /* END CODE */
 
 // [6] Insert "Giraffe" into optionalSet again
 /* BEGIN CODE */
-
+optionalSet?.insert("Giraffe")
 /* END CODE */
 
 // [7] Check if optionalSet contains "Giraffe"
 /* BEGIN CODE */
-
+if let set = optionalSet, set.contains("Giraffe") {
+    print("optionalSet contains Giraffe")
+} else {
+    print("optionalSet does not contain Giraffe")
+}
+print("optionalSet size: \(optionalSet?.count ?? 0)")
 /* END CODE */
 // <-- [RUN HERE] optionalSet SHOULD contain Giraffe at this point
 
@@ -179,7 +195,9 @@ print("optionalSet size: \(optionalSet?.count)")
 
 // [8] Insert "Giraffe" into optionalSet again
 /* BEGIN CODE */
+optionalSet?.insert("Giraffe")
 
+print("optionalSet size: \(optionalSet?.count ?? 0)")
 /* END CODE */
 
 print("optionalSet size: \(optionalSet?.count)")