Add solution #353

Author: JoshCrozier

README.md

@@ -341,6 +341,7 @@
 350|[Intersection of Two Arrays II](./solutions/0350-intersection-of-two-arrays-ii.js)|Easy|
 351|[Android Unlock Patterns](./solutions/0351-android-unlock-patterns.js)|Medium|
 352|[Data Stream as Disjoint Intervals](./solutions/0352-data-stream-as-disjoint-intervals.js)|Hard|
+353|[Design Snake Game](./solutions/0353-design-snake-game.js)|Medium|
 354|[Russian Doll Envelopes](./solutions/0354-russian-doll-envelopes.js)|Hard|
 355|[Design Twitter](./solutions/0355-design-twitter.js)|Medium|
 357|[Count Numbers with Unique Digits](./solutions/0357-count-numbers-with-unique-digits.js)|Medium|

solutions/0353-design-snake-game.js

@@ -0,0 +1,82 @@
+/**
+ * 353. Design Snake Game
+ * https://leetcode.com/problems/design-snake-game/
+ * Difficulty: Medium
+ *
+ * Design a Snake game that is played on a device with screen size height x width. Play the
+ * game online if you are not familiar with the game.
+ *
+ * The snake is initially positioned at the top left corner (0, 0) with a length of 1 unit.
+ *
+ * You are given an array food where food[i] = (ri, ci) is the row and column position of a
+ * piece of food that the snake can eat. When a snake eats a piece of food, its length and
+ * the game's score both increase by 1.
+ *
+ * Each piece of food appears one by one on the screen, meaning the second piece of food will
+ * not appear until the snake eats the first piece of food.
+ *
+ * When a piece of food appears on the screen, it is guaranteed that it will not appear on a
+ * block occupied by the snake.
+ *
+ * The game is over if the snake goes out of bounds (hits a wall) or if its head occupies a
+ * space that its body occupies after moving (i.e. a snake of length 4 cannot run into itself).
+ *
+ * Implement the SnakeGame class:
+ * - SnakeGame(int width, int height, int[][] food) Initializes the object with a screen of size
+ *   height x width and the positions of the food.
+ * - int move(String direction) Returns the score of the game after applying one direction move
+ *   by the snake. If the game is over, return -1.
+ */
+
+/**
+ * @param {number} width
+ * @param {number} height
+ * @param {number[][]} food
+ */
+var SnakeGame = function(width, height, food) {
+  this.width = width;
+  this.height = height;
+  this.food = food;
+  this.foodIndex = 0;
+  this.score = 0;
+  this.snake = [[0, 0]];
+  this.bodySet = new Set(['0,0']);
+};
+
+/**
+ * @param {string} direction
+ * @return {number}
+ */
+SnakeGame.prototype.move = function(direction) {
+  const head = [...this.snake[0]];
+
+  if (direction === 'U') head[0]--;
+  else if (direction === 'D') head[0]++;
+  else if (direction === 'L') head[1]--;
+  else if (direction === 'R') head[1]++;
+
+  if (head[0] < 0 || head[0] >= this.height || head[1] < 0 || head[1] >= this.width) {
+    return -1;
+  }
+
+  const tail = this.snake.pop();
+  this.bodySet.delete(`${tail[0]},${tail[1]}`);
+
+  const headKey = `${head[0]},${head[1]}`;
+  if (this.bodySet.has(headKey)) {
+    return -1;
+  }
+
+  this.snake.unshift(head);
+  this.bodySet.add(headKey);
+
+  if (this.foodIndex < this.food.length && head[0] === this.food[this.foodIndex][0]
+      && head[1] === this.food[this.foodIndex][1]) {
+    this.snake.push(tail);
+    this.bodySet.add(`${tail[0]},${tail[1]}`);
+    this.foodIndex++;
+    this.score++;
+  }
+
+  return this.score;
+};