Baekjoon algorithm 2178

#include <cstdio>
#include <algorithm>
#include <queue>
using namespace std;

const int MAX = 101;
const int dx[] = {-1, 1, 0, 0};
const int dy[] = {0, 0, -1, 1};
queue<pair<int, int>> q;
int mat[MAX][MAX];
int visited[MAX][MAX];
int n, m;
int cnt = 1;

int main() {
	int i, j;
	scanf("%d %d", &n, &m);
	
	for (i=0; i<n; i++) {
		for (j=0; j<m; j++) {
			scanf("%1d", &mat[i][j]);
			visited[i][j] = 0;
		}
	}
	visited[0][0] = 1;
	q.push({0,0});
	
	while(1) {
		int x = q.front().first;
		int y = q.front().second;
		
		q.pop();
		
		if (x == n-1 && y == m-1) {
			printf("%d", visited[n-1][m-1]);
			return 0;
		}
		
		for (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 (visited[nx][ny] == 0 && mat[nx][ny] == 1) {
					q.push({nx, ny});
					visited[nx][ny] = visited[x][y] + 1;
				}
			}
		}
	}
	return 0;
}