Add solution #874

Author: JoshCrozier

README.md

@@ -681,6 +681,7 @@
 871|[Minimum Number of Refueling Stops](./0871-minimum-number-of-refueling-stops.js)|Hard|
 872|[Leaf-Similar Trees](./0872-leaf-similar-trees.js)|Easy|
 873|[Length of Longest Fibonacci Subsequence](./0873-length-of-longest-fibonacci-subsequence.js)|Medium|
+874|[Walking Robot Simulation](./0874-walking-robot-simulation.js)|Medium|
 875|[Koko Eating Bananas](./0875-koko-eating-bananas.js)|Medium|
 876|[Middle of the Linked List](./0876-middle-of-the-linked-list.js)|Easy|
 884|[Uncommon Words from Two Sentences](./0884-uncommon-words-from-two-sentences.js)|Easy|

solutions/0874-walking-robot-simulation.js

@@ -0,0 +1,63 @@
+/**
+ * 874. Walking Robot Simulation
+ * https://leetcode.com/problems/walking-robot-simulation/
+ * Difficulty: Medium
+ *
+ * A robot on an infinite XY-plane starts at point (0, 0) facing north. The robot receives an array
+ * of integers commands, which represents a sequence of moves that it needs to execute. There are
+ * only three possible types of instructions the robot can receive:
+ * - -2: Turn left 90 degrees.
+ * - -1: Turn right 90 degrees.
+ * - 1 <= k <= 9: Move forward k units, one unit at a time.
+ *
+ * Some of the grid squares are obstacles. The ith obstacle is at grid point
+ * obstacles[i] = (xi, yi). If the robot runs into an obstacle, it will stay in its current location
+ * (on the block adjacent to the obstacle) and move onto the next command.
+ *
+ * Return the maximum squared Euclidean distance that the robot reaches at any point in its path
+ * (i.e. if the distance is 5, return 25).
+ *
+ * Note:
+ * - There can be an obstacle at (0, 0). If this happens, the robot will ignore the obstacle until
+ *   it has moved off the origin. However, it will be unable to return to (0, 0) due to the
+ *   obstacle.
+ * - North means +Y direction.
+ * - East means +X direction.
+ * - South means -Y direction.
+ * - West means -X direction.
+ */
+
+/**
+ * @param {number[]} commands
+ * @param {number[][]} obstacles
+ * @return {number}
+ */
+var robotSim = function(commands, obstacles) {
+  const directions = [[0, 1], [1, 0], [0, -1], [-1, 0]];
+  const obstacleSet = new Set(obstacles.map(([x, y]) => `${x},${y}`));
+
+  let x = 0;
+  let y = 0;
+  let directionIndex = 0;
+  let result = 0;
+
+  for (const command of commands) {
+    if (command === -1) {
+      directionIndex = (directionIndex + 1) % 4;
+    } else if (command === -2) {
+      directionIndex = (directionIndex + 3) % 4;
+    } else {
+      const [dx, dy] = directions[directionIndex];
+      for (let step = 0; step < command; step++) {
+        const nextX = x + dx;
+        const nextY = y + dy;
+        if (obstacleSet.has(`${nextX},${nextY}`)) break;
+        x = nextX;
+        y = nextY;
+        result = Math.max(result, x * x + y * y);
+      }
+    }
+  }
+
+  return result;
+};