[Array] Add a solution to Exam Room

Author: soapyigu

Array/ExamRoom.swift

@@ -0,0 +1,51 @@
+/**
+ * Question Link: https://leetcode.com/problems/exam-room/
+ * Primary idea: Calculate and compare middle point between two taken seats.
+ *
+ * Time Complexity: O(n) for seat(), O(1) for leave(at:), Space Complexity: O(n)
+ *
+ */
+
+ class ExamRoom {
+  	var seats: [Int]
+  
+  	init(_ n: Int) {
+    	seats = Array(repeating: 0, count: n)
+  	}
+  
+  	func seat() -> Int {
+    	var maxDistance = 0, maxIndex = 0, lastOne = -1
+    
+    	for (i, seat) in seats.enumerated() {
+	      	if seat == 1 {
+	        	if lastOne == -1 {
+	          		if maxDistance < i {
+	            		maxDistance = i
+	            		maxIndex = 0
+	            	}
+	          	} else {
+	          		if maxDistance < (i - lastOne) / 2 {
+	            		maxDistance = (i - lastOne) / 2
+	            		maxIndex = lastOne + (i - lastOne) / 2
+	          		}
+	          	}
+        	}
+        
+        	lastOne = i
+      	}
+    
+	    if lastOne != -1 {
+	      	if maxDistance < (seats.count - 1 - lastOne) / 2 {
+	        	maxIndex = seats.count - 1
+	      	}
+	    }
+    
+    	seats[maxIndex] = 1
+    
+    	return maxIndex
+  	}
+  
+  	func leave(_ seat: Int) {
+    	seats[seat] = 0
+  	}
+}

README.md

@@ -28,7 +28,7 @@
 * [Microsoft](#microsoft)
 
 ## Progress
-[Problem Status](#problem-status) shows the latest progress to all 800+ questions. Currently we have 260 completed solutions. Note: questions with ♥ mark means that you have to **Subscript to premium membership** of LeetCode to unlock them. Thank you for great contributions from [CharleneJiang](https://github.com/CharleneJiang), [ReadmeCritic](https://github.com/ReadmeCritic), [demonkoo](https://github.com/demonkoo), [DaiYue](https://github.com/DaiYue), [Quaggie](https://github.com/Quaggie) and [jindulys](https://github.com/jindulys).
+[Problem Status](#problem-status) shows the latest progress to all 800+ questions. Currently we have 261 completed solutions. Note: questions with ♥ mark means that you have to **Subscript to premium membership** of LeetCode to unlock them. Thank you for great contributions from [CharleneJiang](https://github.com/CharleneJiang), [ReadmeCritic](https://github.com/ReadmeCritic), [demonkoo](https://github.com/demonkoo), [DaiYue](https://github.com/DaiYue), [Quaggie](https://github.com/Quaggie) and [jindulys](https://github.com/jindulys).
 
 
 ## Array
@@ -56,6 +56,7 @@
 [Summary Ranges](https://leetcode.com/problems/summary-ranges/)| [Swift](./Array/SummaryRanges.swift)| Medium| O(n)| O(n)|
 [Asteroid Collision](https://leetcode.com/problems/asteroid-collision/)| [Swift](./Array/AsteroidCollision.swift)| Medium| O(n)| O(n)|
 [Maximize Distance to Closest Person](https://leetcode.com/problems/maximize-distance-to-closest-person/)| [Swift](./Array/MaximizeDistanceToClosestPerson.swift)| Easy| O(n)| O(1)|
+[Exam Room](https://leetcode.com/problems/exam-room/)| [Swift](./Array/ExamRoom.swift)| Medium| O(n)| O(n)|
 [Shortest Word Distance](https://leetcode.com/problems/shortest-word-distance/)| [Swift](./Array/ShortestWordDistance.swift)| Easy| O(n)| O(1)|
 [Shortest Word Distance III](https://leetcode.com/problems/shortest-word-distance-iii/)| [Swift](./Array/ShortestWordDistanceIII.swift)| Medium| O(n)| O(1)|
 [Minimum Size Subarray Sum](https://leetcode.com/problems/minimum-size-subarray-sum/)| [Swift](./Array/MinimumSizeSubarraySum.swift)| Medium| O(n)| O(1)|