백준 1743번 음식물 피하기 C++

출처 : https://www.acmicpc.net/problem/1743

 

bfs/dfs 방식으로 탐색하면서 가장 큰 뭉쳐있는 쓰레기를 찾는 문제이다. 대각선으로는 못가고, 상하좌우로만 탐색하면 된다.

 

#include <iostream>
#include <string>
#include <vector>
#include <math.h>
#include <algorithm>
#include <utility>
#include <stack>
#include <queue>
#include <math.h>
#include <set>
#include <map>
#include <unordered_map>
#include <unordered_set>

using namespace std;
typedef long long ll;

int n, m, k;
int max_trash = 0;
vector<vector<bool>> trash(100, vector<bool>(100, false));

int posR[4] = { -1,0,1,0 };
int posC[4] = { 0,1,0,-1 };

void bfs() {
	queue<pair<int, int>> q;
	for (int i = 0; i < n; i++) {
		for (int j = 0; j < m; j++) {
			if (trash[i][j]) {
				int size = 0;
				q.push({ i,j });
				trash[i][j] = false;
				while (!q.empty()) {
					auto a = q.front();
					q.pop();
					size++;
					for (int i = 0; i < 4; i++) {
						int nextRow = a.first + posR[i];
						int nextCol = a.second + posC[i];
						if (nextRow < 0 || nextRow >= n) continue;
						if (nextCol < 0 || nextCol >= m) continue;
						if (!trash[nextRow][nextCol]) continue;
						q.push({ nextRow, nextCol });
						trash[nextRow][nextCol] = false;
					}
				}
				max_trash = max(max_trash, size);
			}
		}
	}
}

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	cout.tie(NULL);
	
	cin >> n >> m >> k;
	int row, col;
	
	for (int i = 0; i < k; i++) {
		cin >> row >> col;
		trash[row - 1][col - 1] = true;
	}
	bfs();
	cout << max_trash;
};