Algorithm
Problem Name: 874. Walking Robot Simulation
A robot on an infinite XY-plane starts at point (0, 0) facing north. The robot can receive a sequence of these three possible types of commands:
-2: Turn left90degrees.-1: Turn right90degrees.1 <= k <= 9: Move forwardkunits, 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, then it will instead stay in its current location and move on to the next command.
Return the maximum Euclidean distance that the robot ever gets from the origin squared (i.e. if the distance is 5, return 25).
Note:
- North means +Y direction.
- East means +X direction.
- South means -Y direction.
- West means -X direction.
Example 1:
Input: commands = [4,-1,3], obstacles = [] Output: 25 Explanation: The robot starts at (0, 0): 1. Move north 4 units to (0, 4). 2. Turn right. 3. Move east 3 units to (3, 4). The furthest point the robot ever gets from the origin is (3, 4), which squared is 32 + 42 = 25 units away.
Example 2:
Input: commands = [4,-1,4,-2,4], obstacles = [[2,4]] Output: 65 Explanation: The robot starts at (0, 0): 1. Move north 4 units to (0, 4). 2. Turn right. 3. Move east 1 unit and get blocked by the obstacle at (2, 4), robot is at (1, 4). 4. Turn left. 5. Move north 4 units to (1, 8). The furthest point the robot ever gets from the origin is (1, 8), which squared is 12 + 82 = 65 units away.
Example 3:
Input: commands = [6,-1,-1,6], obstacles = [] Output: 36 Explanation: The robot starts at (0, 0): 1. Move north 6 units to (0, 6). 2. Turn right. 3. Turn right. 4. Move south 6 units to (0, 0). The furthest point the robot ever gets from the origin is (0, 6), which squared is 62 = 36 units away.
Constraints:
1 <= commands.length <= 104commands[i]is either-2,-1, or an integer in the range[1, 9].0 <= obstacles.length <= 104-3 * 104 <= xi, yi <= 3 * 104- The answer is guaranteed to be less than
231.
Code Examples
#1 Code Example with Javascript Programming
Code -
Javascript Programming
const robotSim = function(commands, obstacles) {
const dirs = [[1, 0], [0, -1], [-1, 0], [0, 1]] // east, south, west, north
const set = new Set()
obstacles.forEach(([x, y]) => set.add(`${x},${y}`))
let idx = 3, x = 0, y = 0, res = 0
for(let e of commands) {
if(e === -2) idx = (3 + idx) % 4
else if(e === -1) idx = (1 + idx) % 4
else {
const [dx, dy] = dirs[idx]
let dis = 0
while(dis < e) {
const nx = x + dx, ny = y + dy
const k = `${nx},${ny}`
if(set.has(k)) break
x = nx
y = ny
dis++
res = Math.max(res, x * x + y * y>
}
}
}
return res
};
Input
Output
#2 Code Example with Python Programming
Code -
Python Programming
class Solution:
def robotSim(self, commands, obstacles):
i = j = mx = 0
d, move, obstacles = 3, [(-1, 0), (0, -1), (1, 0), (0, 1)], set(map(tuple, obstacles))
for command in commands:
if command == -2: d = (d + 1) % 4
elif command == -1: d = (d - 1) % 4
else:
x, y = move[d]
while command and (i + x, j + y) not in obstacles:
i += x
j += y
command -= 1
mx = max(mx, i ** 2 + j ** 2)
return mx
Input
Output
#3 Code Example with C# Programming
Code -
C# Programming
using System;
using System.Collections.Generic;
namespace LeetCode
{
public class _0874_WalkingRobotSimulation
{
public int RobotSim(int[] commands, int[][] obstacles)
{
int[] dx = new int[] { 0, 1, 0, -1 }, dy = new int[] { 1, 0, -1, 0 };
int x = 0, y = 0, dir = 0;
var obstacleSet = new HashSet < int>();
foreach (var obstacle in obstacles)
obstacleSet.Add((obstacle[0] << 16) + obstacle[1]);
var result = 0;
foreach (var cmd in commands)
{
if (cmd == -2) dir = (dir + 3) % 4;
else if (cmd == -1) dir = (dir + 1) % 4;
else
{
for (int i = 0; i < cmd; i++)
{
var nx = x + dx[dir];
var ny = y + dy[dir];
if (obstacleSet.Contains((nx << 16) + ny))
break;
x = nx;
y = ny;
}
}
result = Math.Max(result, x * x + y * y);
}
return result;
}
}
}
Input
Output