CS Unit 2 Build: Interview Prep 1

Practice-Problems/CSPracticeProblems.playground/Contents.swift

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+// 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
+
+//---------------------------------------------------------------------------------------------
+
+// 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
+}
+
+//---------------------------------------------------------------------------------------------

Practice-Problems/CSPracticeProblems.playground/contents.xcplayground

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+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<playground version='5.0' target-platform='ios' buildActiveScheme='true'>
+    <timeline fileName='timeline.xctimeline'/>
+</playground>