[TIL] 211021

1. 백준

• 2667번

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;

#define MAX 26
string map[MAX];
int n;
int cnt = 0;
int dx[4] = { -1, 1, 0, 0 };
int dy[4] = { 0, 0,-1,1 };
vector<int> v;

void dfs(int x, int y) {
	map[x][y] = '0';
	cnt++;
	for (int i = 0; i < 4; i++) {
		int nx = x + dx[i];
		int ny = y + dy[i];
		if (nx >= 0 && nx < n && ny >= 0 && ny < n) {
			if (map[nx][ny] == '1') {
				dfs(nx, ny);
			}
		}
	}
}

int main() {
	cin >> n;
	for (int i = 0; i < n; i++) {
		cin >> map[i];
	}

	for (int i = 0; i < n; i++) {
		for (int j = 0; j < n; j++) {
			if (map[i][j] == '1') {
				dfs(i, j);
				v.push_back(cnt);
				cnt = 0;
			}
		}
	}
	cout << v.size() << "\n";
	sort(v.begin(), v.end());
	for (int i = 0; i < v.size(); i++) {
		cout << v[i] << "\n";
	}
}

💡 string으로 받아오므로 문자와 비교하기

• 1012번

#include <iostream>
#include <string.h>
using namespace std;

#define MAX 51

int map[MAX][MAX] = { 0, };
bool visited[MAX][MAX] = { false, };
int T, M, N, K;
//int n;
int cnt = 0;
int dx[4] = { -1, 1, 0, 0 };
int dy[4] = { 0, 0,-1,1 };

void dfs(int x, int y) {
	visited[x][y] = true;
	//cnt++;
	for (int i = 0; i < 4; i++) {
		int nx = x + dx[i];
		int ny = y + dy[i];
		if (nx >= 0 && nx < N && ny >= 0 && ny < M) {
			if (map[nx][ny] == 1 && !visited[nx][ny]) {
				dfs(nx, ny);
			}
		}
	}
}

int main() {
	cin >> T;
	while (T > 0) {
		cnt = 0;
		cin >> M >> N >> K;
		for (int i = 0; i < K; i++) {
			int a, b;
			cin >> a >> b;
			map[b][a] = 1;
		}
		for (int i = 0; i < N; i++) {
			for (int j = 0; j < M; j++) {
				if (map[i][j] == 1 && !visited[i][j]) {
					dfs(i, j);
					cnt++;
					
				}
			}
		}
		cout << cnt << "\n";
		T--;
		memset(visited, false, sizeof(visited));
		memset(map, 0, sizeof(map));
	}
	
}

💡 memset
배열 초기화를 위해 씀, memset(배열이름, 초기화할 값, 사이즈)

#include <string.h>

를 써주어야 한다.