From d96abb6ca655d2c53e47ea087b08219818921cbe Mon Sep 17 00:00:00 2001
From: David Wright <davidtwright89@gmail.com>
Date: Wed, 14 Oct 2020 23:59:04 -0400
Subject: [PATCH 1/3] Added a playground for solving coding interview practice
 problems

---
 .../CSPracticeProblems.playground/Contents.swift           | 1 +
 .../CSPracticeProblems.playground/contents.xcplayground    | 4 ++++
 .../playground.xcworkspace/contents.xcworkspacedata        | 7 +++++++
 3 files changed, 12 insertions(+)
 create mode 100644 Practice-Problems/CSPracticeProblems.playground/Contents.swift
 create mode 100644 Practice-Problems/CSPracticeProblems.playground/contents.xcplayground
 create mode 100644 Practice-Problems/CSPracticeProblems.playground/playground.xcworkspace/contents.xcworkspacedata

diff --git a/Practice-Problems/CSPracticeProblems.playground/Contents.swift b/Practice-Problems/CSPracticeProblems.playground/Contents.swift
new file mode 100644
index 00000000..ba8bb2dd
--- /dev/null
+++ b/Practice-Problems/CSPracticeProblems.playground/Contents.swift
@@ -0,0 +1 @@
+// LeetCode Practice Problems: Algorithms
diff --git a/Practice-Problems/CSPracticeProblems.playground/contents.xcplayground b/Practice-Problems/CSPracticeProblems.playground/contents.xcplayground
new file mode 100644
index 00000000..a751024c
--- /dev/null
+++ b/Practice-Problems/CSPracticeProblems.playground/contents.xcplayground
@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>
\ No newline at end of file
diff --git a/Practice-Problems/CSPracticeProblems.playground/playground.xcworkspace/contents.xcworkspacedata b/Practice-Problems/CSPracticeProblems.playground/playground.xcworkspace/contents.xcworkspacedata
new file mode 100644
index 00000000..919434a6
--- /dev/null
+++ b/Practice-Problems/CSPracticeProblems.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>

From 47bbddad77405ac816525563739b3527c4ec98af Mon Sep 17 00:00:00 2001
From: David Wright <davidtwright89@gmail.com>
Date: Thu, 15 Oct 2020 00:00:36 -0400
Subject: [PATCH 2/3] Added a binary search problem

---
 .../Contents.swift                            | 44 +++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/Practice-Problems/CSPracticeProblems.playground/Contents.swift b/Practice-Problems/CSPracticeProblems.playground/Contents.swift
index ba8bb2dd..1819d953 100644
--- a/Practice-Problems/CSPracticeProblems.playground/Contents.swift
+++ b/Practice-Problems/CSPracticeProblems.playground/Contents.swift
@@ -1 +1,45 @@
 // LeetCode Practice Problems: Algorithms
+
+//---------------------------------------------------------------------------------------------
+
+// MARK: - Binary Search Problems
+// Key Words: sorted, range
+// Notes:
+//   - Binary search should be muscle memory
+//   - Can be implemented iteratively or recursively
+
+//---------------------------------------------------------------------------------------------
+
+// Sqrt(x)
+// Compute and return the square root of x, where x is guaranteed to be a non-negative integer.
+// Since the return type is an integer, the decimal digits are truncated and only the integer
+// part of the result is returned.
+
+func squareRoot(_ x: Int) -> Int {
+    var min = 0
+    var max = x
+    var res = 0
+    
+    while min <= max {
+        let mid = Int((min + max) / 2)
+        let squared = mid * mid
+        if squared == x {
+            return mid
+        } else if squared > x {
+            max = mid - 1
+        } else {
+            min = mid + 1
+            res = mid
+        }
+    }
+    
+    return res
+}
+
+print(squareRoot(16))   // 4
+print(squareRoot(9))    // 3
+print(squareRoot(8))    // 2
+print(squareRoot(1))    // 1
+print(squareRoot(0))    // 0
+
+//---------------------------------------------------------------------------------------------

From 929d41fb8c997934d8e4f9d9aa91d2c5020aeb5b Mon Sep 17 00:00:00 2001
From: David Wright <davidtwright89@gmail.com>
Date: Thu, 15 Oct 2020 00:01:15 -0400
Subject: [PATCH 3/3] Added a hash table problem

---
 .../Contents.swift                            | 28 +++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/Practice-Problems/CSPracticeProblems.playground/Contents.swift b/Practice-Problems/CSPracticeProblems.playground/Contents.swift
index 1819d953..bd7f7037 100644
--- a/Practice-Problems/CSPracticeProblems.playground/Contents.swift
+++ b/Practice-Problems/CSPracticeProblems.playground/Contents.swift
@@ -43,3 +43,31 @@ print(squareRoot(1))    // 1
 print(squareRoot(0))    // 0
 
 //---------------------------------------------------------------------------------------------
+
+// MARK: - Hash Table Problems
+// Key Words: two arrays, intersection, count
+
+//---------------------------------------------------------------------------------------------
+
+// Intersection of Two Arrays II
+// Given two arrays, write a function to compute their intersection.
+
+func intersect(_ nums1: [Int], _ nums2: [Int]) -> [Int] {
+    var res: [Int] = []
+    var dict = [Int: Int]()
+    
+    for n1 in nums1 {
+        dict[n1, default: 0] += 1
+    }
+    
+    for n2 in nums2 {
+        if dict[n2, default: 0] > 0 {
+            res.append(n2)
+            dict[n2]! -= 1
+        }
+    }
+    
+    return res
+}
+
+//---------------------------------------------------------------------------------------------