Leetcode 353 Solution

class SnakeGame {
    queue<pair<int, int>> q;
    set<pair<int, int>> snake;
    queue<pair<int, int>> foods;
    int m_width;
    int m_height;

public:
    /** Initialize your data structure here.
        @param width - screen width
        @param height - screen height 
        @param food - A list of food positions
        E.g food = [[1,1], [1,0]] means the first food is positioned at [1,1], the second is at [1,0]. */
    SnakeGame(int width, int height, vector<pair<int, int>> food) {
        m_width = width;
        m_height = height;
        q.push(make_pair(0, 0));
        snake.insert(make_pair(0, 0));
        for (auto pair : food)
            foods.push(pair);
    }
    
    /** Moves the snake.
        @param direction - 'U' = Up, 'L' = Left, 'R' = Right, 'D' = Down 
        @return The game's score after the move. Return -1 if game over. 
        Game over when snake crosses the screen boundary or bites its body. */
    int move(string direction) {
        auto head = q.back();
        auto next = head;
        
        if (direction == "U")
            next.first--;
        else if (direction == "L")
            next.second--;
        else if (direction == "R")
            next.second++;
        else if (direction == "D")
            next.first++;
        
        if (next.first < 0 || next.first >= m_height || next.second < 0 || next.second >= m_width)
            return -1;
        
        if (snake.find(next) != snake.end() && next != q.front())
            return -1;

        if (foods.empty() == false && foods.front() == next)
        {
            snake.insert(next);
            q.push(next);
            foods.pop();
        }
        else
        {
            snake.erase(q.front());
            q.pop();
            snake.insert(next);
            q.push(next);
        }

        return q.size() - 1;
    }
};

/**
 * Your SnakeGame object will be instantiated and called as such:
 * SnakeGame obj = new SnakeGame(width, height, food);
 * int param_1 = obj.move(direction);
 */