백준 - 단지번호붙이기 [2667]

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;
char map[25][25]; 
char map2[25][25];
vector<int> result;
int num;
int mapping(int i, int j, int island_num);

int main() {
	
	int size = 0;
	int island_num = 1;

	cin >> size;

	for (int i = 0; i < size; i++) {
		cin >> map[i];
	}
	for (int i = 0; i < size; i++)
		for (int j = 0; j < size; j++)
			map2[i][j] = '0';

	for (int i = 0; i < size; i++)
		for (int j = 0; j < size; j++)
			if (map[i][j] == '1' && map2[i][j] == '0') {
				result.push_back(mapping(i,j,island_num));
				num = 0;
				island_num++;
			}
	cout << island_num - 1 << endl;

	sort(result.begin(), result.end());

	for (int i = 0; i < (int)result.size(); i++)
		if(result[i]!=-1)
		cout << result[i] << endl;
	
	return 0;
}


int mapping(int i, int j, int island_num) {

	if (map2[i][j] != '0')
		return -1;

	map2[i][j] = 1;
	num++;

	if (i > 0 && map[i - 1][j] == '1' && map2[i-1][j] == '0') {
		mapping(i-1, j, island_num);
	}
	
	if (j>0 && map[i][j - 1] == '1' && map2[i][j-1] == '0') {
		mapping(i, j - 1, island_num);
	}

	if (j+1<25 && map[i][j + 1] == '1' && map2[i][j+1] == '0') {
		mapping(i, j + 1, island_num);
	}

	if (i+1<25 && map[i+1][j] == '1' && map2[i + 1][j] == '0') {
		mapping(i+1, j, island_num);
	}

	return num;
}