Path in Matrix

• Time : $O(nm)$
• Space : $O(nm)$

int Solution::checkPath(vector<vector<int> > &A) {
    queue<pair<int, int>> q;
    int n = A.size(), m = A[0].size();
    int dy[4]{-1,0,1,0}, dx[4]{0,1,0,-1};
    for(int i = 0; i < n; i++) for(int j = 0; j < m; j++) {
        if(A[i][j] == 1) q.push({i,j});
    }
    while(q.size()) {
        auto [y,x] = q.front(); q.pop();
        for(int i = 0; i < 4; i++) {
            int ny = y + dy[i], nx = x + dx[i];
            if(0 <= ny and ny < n and 0 <= nx and nx < m and A[ny][nx]) {
                if(A[ny][nx] == 2) return 1;
                A[ny][nx] = 0;
                q.push({ny,nx});
            }
        }
    }
    return false;
}