[c++] 아이템줍기 (BFS)

#include <string>
#include <vector>
#include <queue>
#include <utility>
using namespace std;
#define pii pair<int,int >
#define piii pair<int, pii > 
vector<vector<int>> rec;
int n;
int dy[4]={0,1,0,-1};
int dx[4]={1,0,-1,0};
int board[200][200];
int fx,fy;
 
 
void BFS(int x,int y){
    queue<pii > q;
    q.push({x,y});
 
    while(!q.empty()){
        int x=q.front().first;
        int y=q.front().second;
        q.pop();
        if(x==fx && y==fy)
            return ;
        for(int i=0;i<4;i++){
            int nx=x+dx[i];
            int ny=y+dy[i];
            if(board[nx][ny]==1 ){
                board[nx][ny]=board[x][y]+1;
                q.push({nx,ny});
            }
        }
    }
}
 
int solution(vector<vector<int>> rectangle, int characterX, int characterY, int itemX, int itemY) {
    int answer = 0;
    n=rectangle.size();
    fx=itemX*2;
    fy=itemY*2;
    characterX *= 2, characterY *= 2;
    rec.resize(n,vector<int>(4));
    int x1, y1, x2, y2;
    for(int i=0;i<n;i++){
        for(int j=0;j<4;j++){
            rec[i][j]=rectangle[i][j]*2;
        }
        x1 = rec[i][0], y1 = rec[i][1];
        x2 = rec[i][2], y2 = rec[i][3];
        for(int i=x1; i<=x2;i++)
            for(int j=y1; j<=y2; j++)
                board[i][j]=1;
    }
    for (int i = 0; i < n; i++) {
        x1 = rec[i][0], y1 = rec[i][1];
        x2 = rec[i][2], y2 = rec[i][3];
        for (int i = x1 + 1; i < x2; i++)
            for (int j = y1 + 1; j < y2; j++)
                board[i][j] = 0;
    }
 
    
    BFS(characterX,characterY);
    return board[fx][fy]/2 ;
}
 

출처:https://school.programmers.co.kr/learn/courses/30/lessons/87694?language=cpp