백준 2667번 단지번호 붙이기 [C++]

<코드>

#include <cstdio>
#include <algorithm>
#include <queue>
using namespace std;
int a[30][30];
int group[30][30];
int dx[] = {0,0,1,-1};
int dy[] = {1,-1,0,0};
int n;
int ans[25*25];
void bfs(int x, int y, int cnt) {
    queue<pair<int,int>> q;
    q.push(make_pair(x,y));
    group[x][y] = cnt;
    while (!q.empty()) {
        x = q.front().first;
        y = q.front().second;
        q.pop();
        for (int k=0; k<4; k++) {
            int nx = x+dx[k];
            int ny = y+dy[k];
            if (0 <= nx && nx < n && 0 <= ny && ny < n) {
                if (a[nx][ny] == 1 && group[nx][ny] == 0) {
                    q.push(make_pair(nx,ny));
                    group[nx][ny] = cnt;
                }
            }
        }
    }
}
int main() {
    scanf("%d",&n);
    for (int i=0; i<n; i++) {
        for (int j=0; j<n; j++) {
            scanf("%1d",&a[i][j]);
        }
    }
    int cnt = 0;
    for (int i=0; i<n; i++) {
        for (int j=0; j<n; j++) {
            if (a[i][j] == 1 && group[i][j] == 0) {
                bfs(i, j, ++cnt);
            }
        }
    }
    printf("%d\n",cnt);
    for (int i=0; i<n; i++) {
        for (int j=0; j<n; j++) {
            ans[group[i][j]]+=1;
        }
    }
    sort(ans+1, ans+cnt+1);
    for (int i=1; i<=cnt; i++) {
        printf("%d\n",ans[i]);
    }
    return 0;
}

2667번: 단지번호붙이기 (acmicpc.net)