<p>A robot on an infinite XY-plane starts at point <code>(0, 0)</code> facing north. The robot receives an array of integers <code>commands</code>, which represents a sequence of moves that it needs to execute. There are only three possible types of instructions the robot can receive:</p>

<ul>
	<li><code>-2</code>: Turn left <code>90</code> degrees.</li>
	<li><code>-1</code>: Turn right <code>90</code> degrees.</li>
	<li><code>1 &lt;= k &lt;= 9</code>: Move forward <code>k</code> units, one unit at a time.</li>
</ul>

<p>Some of the grid squares are <code>obstacles</code>. The <code>i<sup>th</sup></code> obstacle is at grid point <code>obstacles[i] = (x<sub>i</sub>, y<sub>i</sub>)</code>. 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.</p>

<p>Return the <strong>maximum squared Euclidean distance</strong> that the robot reaches at any point in its path (i.e. if the distance is <code>5</code>, return <code>25</code>).</p>

<p><strong>Note:</strong></p>

<ul>
	<li>There can be an obstacle at <code>(0, 0)</code>. If this happens, the robot will ignore the obstacle until it has moved off the origin. However, it will be unable to return to <code>(0, 0)</code> due to the obstacle.</li>
	<li>North means +Y direction.</li>
	<li>East means +X direction.</li>
	<li>South means -Y direction.</li>
	<li>West means -X direction.</li>
</ul>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">commands = [4,-1,3], obstacles = []</span></p>

<p><strong>Output:</strong> <span class="example-io">25</span></p>

<p><strong>Explanation: </strong></p>

<p>The robot starts at <code>(0, 0)</code>:</p>

<ol>
	<li>Move north 4 units to <code>(0, 4)</code>.</li>
	<li>Turn right.</li>
	<li>Move east 3 units to <code>(3, 4)</code>.</li>
</ol>

<p>The furthest point the robot ever gets from the origin is <code>(3, 4)</code>, which squared is <code>3<sup>2</sup> + 4<sup>2 </sup>= 25</code> units away.</p>
</div>

<p><strong class="example">Example 2:</strong></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">commands = [4,-1,4,-2,4], obstacles = [[2,4]]</span></p>

<p><strong>Output:</strong> <span class="example-io">65</span></p>

<p><strong>Explanation:</strong></p>

<p>The robot starts at <code>(0, 0)</code>:</p>

<ol>
	<li>Move north 4 units to <code>(0, 4)</code>.</li>
	<li>Turn right.</li>
	<li>Move east 1 unit and get blocked by the obstacle at <code>(2, 4)</code>, robot is at <code>(1, 4)</code>.</li>
	<li>Turn left.</li>
	<li>Move north 4 units to <code>(1, 8)</code>.</li>
</ol>

<p>The furthest point the robot ever gets from the origin is <code>(1, 8)</code>, which squared is <code>1<sup>2</sup> + 8<sup>2</sup> = 65</code> units away.</p>
</div>

<p><strong class="example">Example 3:</strong></p>

<div class="example-block">
<p><strong>Input:</strong> <span class="example-io">commands = [6,-1,-1,6], obstacles = [[0,0]]</span></p>

<p><strong>Output:</strong> <span class="example-io">36</span></p>

<p><strong>Explanation:</strong></p>

<p>The robot starts at <code>(0, 0)</code>:</p>

<ol>
	<li>Move north 6 units to <code>(0, 6)</code>.</li>
	<li>Turn right.</li>
	<li>Turn right.</li>
	<li>Move south 5 units and get blocked by the obstacle at <code>(0,0)</code>, robot is at <code>(0, 1)</code>.</li>
</ol>

<p>The furthest point the robot ever gets from the origin is <code>(0, 6)</code>, which squared is <code>6<sup>2</sup> = 36</code> units away.</p>
</div>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= commands.length &lt;= 10<sup>4</sup></code></li>
	<li><code>commands[i]</code> is either <code>-2</code>, <code>-1</code>, or an integer in the range <code>[1, 9]</code>.</li>
	<li><code>0 &lt;= obstacles.length &lt;= 10<sup>4</sup></code></li>
	<li><code>-3 * 10<sup>4</sup> &lt;= x<sub>i</sub>, y<sub>i</sub> &lt;= 3 * 10<sup>4</sup></code></li>
	<li>The answer is guaranteed to be less than <code>2<sup>31</sup></code>.</li>
</ul>

class Solution {
public:
    int move[4][2] = {{0, 1}, {-1, 0}, {0, -1}, {1, 0}}; // left : +1, right : -1
    int robotSim(vector<int>& commands, vector<vector<int>>& obstacles) {
        int max_dist = 0;
        int curr_move = 0;
        map<int, set<int>> obs_xy_map, obs_yx_map;
        for (vector<int> obs : obstacles) {
            obs_xy_map[obs[0]].insert(obs[1]);
            obs_yx_map[obs[1]].insert(obs[0]);
        }

        int curr_x = 0, curr_y = 0;
        for(int cmd : commands) {
            if (cmd > 0) {
                if (curr_move % 2) {
                    set<int> curr_obs_list = obs_yx_map[curr_y];
                    int next_x = curr_x + move[curr_move][0] * cmd;
                    if (curr_move == 1) {
                        for(auto riter = curr_obs_list.rbegin(); riter != curr_obs_list.rend(); riter++) {
                            if (curr_x > (*riter) && next_x <= (*riter)) {
                                next_x = (*riter) + 1;
                                break;
                            }
                        }
                    }
                    else if (curr_move == 3) {
                        for(auto iter = curr_obs_list.begin(); iter != curr_obs_list.end(); iter++) {
                            if (curr_x < (*iter) && next_x >= (*iter)) {
                                next_x = (*iter) - 1;
                                break;
                            }
                        }
                    }
                    curr_x = next_x;
                    
                }
                else {
                    set<int> curr_obs_list = obs_xy_map[curr_x];
                    int next_y = curr_y + move[curr_move][1] * cmd;
                    if (curr_move == 2) {
                        for(auto riter = curr_obs_list.rbegin(); riter != curr_obs_list.rend(); riter++) {
                            if (curr_y > (*riter) && next_y <= (*riter)) {
                                next_y = (*riter) + 1;
                                break;
                            }
                        }
                    }
                    else if (curr_move == 0) {
                        for(auto iter = curr_obs_list.begin(); iter != curr_obs_list.end(); iter++) {
                            if (curr_y < (*iter) && next_y >= (*iter)) {
                                next_y = (*iter) - 1;
                                break;
                            }
                        }
                    }
                    curr_y = next_y;
                }

                int curr_dist = curr_x * curr_x + curr_y * curr_y;
                if (max_dist < curr_dist) {
                    max_dist = curr_dist;
                }
            }
            else {
                if (cmd == -2) {
                    curr_move = (curr_move + 1) % 4;
                }
                if (cmd == -1) {
                    curr_move = (curr_move + 3) % 4;
                }
            }
        }
        
        return max_dist;
    }
};
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