[백준 2573] 빙산 (BFS) (C/C++) (★)

#include <stdio.h>
#include <iostream>
#include <queue>
#include <string.h>
using namespace std;
 
int map[310][310];
int mapCopy[310][310];
int visited[310][310];
int row, col;
int time;
 
queue<pair<int, int>> q;
 
int dx[4] = {-1, 1, 0, 0};
int dy[4] = {0, 0, -1, 1};
 
int safe(int x, int y)
{
    if(x >= 0 && y >= 0 && x < row && y < col)
    {
        return 1;
    }
    else
    {
        return 0;
    }
}
 
void init()
{
    for(int x = 0; x < row; x++)
    {
        for(int y = 0; y < col; y++)
        {
            int cnt = 0;
            
            for(int k = 0; k < 4; k++)
            {
                int xpos = x+dx[k];
                int ypos = y+dy[k];
                
                if(safe(xpos, ypos) == 1 && map[xpos][ypos] == 0)
                {
                    cnt++;        
                }
            }
            
            if(cnt != 0)
            {
                q.push({x, y});
            }
        }
    }
}
 
void melt()
{
    int size = q.size();
    
    while(size--)
    {
        int x = q.front().first;
        int y = q.front().second;
        q.pop();
        
        int cnt = 0;
        
        for(int i = 0; i < 4; i++)
        {
            int xpos = x+dx[i];
            int ypos = y+dy[i];
            
            if(safe(xpos, ypos) == 1 && map[xpos][ypos] == 0)
            {
                cnt++;
            }    
        }    
        
        mapCopy[x][y] -= cnt;
        
        if(mapCopy[x][y] < 0)
        {
            mapCopy[x][y] = 0;
        }    
    }
}
 
void check(int x, int y)
{
    queue<pair<int, int>> c;
    c.push({x, y});
    visited[x][y] = 1;
    
    while(!c.empty())
    {
        x = c.front().first;
        y = c.front().second;
        c.pop();
        
        for(int i = 0; i < 4; i++)
        {
            int xpos = x+dx[i];
            int ypos = y+dy[i];
            
            if(safe(xpos, ypos) == 1 && map[xpos][ypos] != 0 && visited[xpos][ypos] == 0)
            {
                c.push({xpos, ypos});
                visited[xpos][ypos] = 1;
            }
        }
    }
}
 
int main(void)
{
//    freopen("B2589_input.txt", "r", stdin);
    
    cin >> row >> col;
    
    for(int i = 0; i < row; i++)
    {
        for(int j = 0; j < col; j++)
        {
            cin >> map[i][j];
            
            mapCopy[i][j] = map[i][j];
        }
    }
    
    while(1)
    {    
        time++;
        
        init();
        
        melt();
        
        for(int i = 0; i < row; i++)
        {
            for(int j = 0; j < col; j++)
            {
                map[i][j] = mapCopy[i][j];
            }
        }
        
        int mapCnt = 0;
        memset(visited, 0, sizeof(visited));
        for(int i = 0; i < row; i++)
        {
            for(int j = 0; j < col; j++)
            {
                if(map[i][j] != 0 && visited[i][j] == 0)
                {
                    check(i, j);
                    mapCnt++;
                }
            }
        }
        
        if(mapCnt >= 2)
        {
            cout << time;
            break;
        }
        else if(mapCnt == 0)
        {
            cout << "0";
            break;
        }
    }
    
    return 0;
}