Add solution #855

Author: JoshCrozier

README.md

@@ -662,6 +662,7 @@
 852|[Peak Index in a Mountain Array](./0852-peak-index-in-a-mountain-array.js)|Medium|
 853|[Car Fleet](./0853-car-fleet.js)|Medium|
 854|[K-Similar Strings](./0854-k-similar-strings.js)|Hard|
+855|[Exam Room](./0855-exam-room.js)|Medium|
 867|[Transpose Matrix](./0867-transpose-matrix.js)|Easy|
 868|[Binary Gap](./0868-binary-gap.js)|Easy|
 872|[Leaf-Similar Trees](./0872-leaf-similar-trees.js)|Easy|

solutions/0855-exam-room.js

@@ -0,0 +1,88 @@
+/**
+ * 855. Exam Room
+ * https://leetcode.com/problems/exam-room/
+ * Difficulty: Medium
+ *
+ * There is an exam room with n seats in a single row labeled from 0 to n - 1.
+ *
+ * When a student enters the room, they must sit in the seat that maximizes the distance to the
+ * closest person. If there are multiple such seats, they sit in the seat with the lowest number.
+ * If no one is in the room, then the student sits at seat number 0.
+ *
+ * Design a class that simulates the mentioned exam room.
+ *
+ * Implement the ExamRoom class:
+ * - ExamRoom(int n) Initializes the object of the exam room with the number of the seats n.
+ * - int seat() Returns the label of the seat at which the next student will set.
+ * - void leave(int p) Indicates that the student sitting at seat p will leave the room. It is
+ *   guaranteed that there will be a student sitting at seat p.
+ */
+
+/**
+ * @param {number} n - Number of seats in the exam room
+ */
+var ExamRoom = function(n) {
+  this.n = n;
+  this.seats = [];
+};
+
+/**
+ * @return {number}
+ */
+ExamRoom.prototype.seat = function() {
+  if (this.seats.length === 0) {
+    this.seats.push(0);
+    return 0;
+  }
+
+  let maxDistance = this.seats[0];
+  let chosenSeat = 0;
+
+  for (let i = 1; i < this.seats.length; i++) {
+    const distance = Math.floor((this.seats[i] - this.seats[i-1]) / 2);
+    if (distance > maxDistance) {
+      maxDistance = distance;
+      chosenSeat = Math.floor((this.seats[i] + this.seats[i-1]) / 2);
+    }
+  }
+
+  const endDistance = this.n - 1 - this.seats[this.seats.length - 1];
+  if (endDistance > maxDistance) {
+    chosenSeat = this.n - 1;
+    maxDistance = endDistance;
+  }
+
+  const insertPosition = this.findInsertPosition(chosenSeat);
+  this.seats.splice(insertPosition, 0, chosenSeat);
+
+  return chosenSeat;
+};
+
+/**
+ * @param {number} p
+ * @return {void}
+ */
+ExamRoom.prototype.leave = function(p) {
+  const index = this.seats.indexOf(p);
+  this.seats.splice(index, 1);
+};
+
+/**
+ * @param {number} seat
+ * @return {number}
+ */
+ExamRoom.prototype.findInsertPosition = function(seat) {
+  let left = 0;
+  let right = this.seats.length - 1;
+
+  while (left <= right) {
+    const mid = Math.floor((left + right) / 2);
+    if (this.seats[mid] < seat) {
+      left = mid + 1;
+    } else {
+      right = mid - 1;
+    }
+  }
+
+  return left;
+};