hey im getting segmentation fault in below code for rat in a maze problem

Question

the standard rat in maze problem is given a binary grid if grid[i][j]==0 path blocked rat is in 0,0 find all ways to reach n-1,n-1 cell. I have put all the constraints I guess.

 class Solution{ public: // vector<string>ans; // vector<pair<int,int>>dir={{0,1},{0,-1},{-1,0},{1,0}}; // vector<string>move={"R","L","U","D"}; void dfs(int i,int j,vector<vector<int>>&m,string curr,vector<vector<int>>&visited,vector<pair<int,int>>dir,vector<string>move,vector<string>&ans){ if(i==m.size()-1 and j==m.size()-1){ ans.push_back(curr); return; } for(int z=0;z<dir.size();z++ ){ int nx=i+dir[z].first; int ny=j+dir[z].second; if(visited[nx][ny]==0 and m[nx][ny]==1 and nx>=0 and nx<m.size() and ny>=0 and ny<m.size() ){ visited[nx][ny]=1; dfs(nx,ny,m,curr+move[z],visited,dir,move,ans); visited[nx][ny]=0; } } } vector<string> findPath(vector<vector<int>> &m, int n) { vector<vector<int>>visited(m.size(),vector<int>(n,0)); string curr=""; vector<string>ans; vector<pair<int,int>>dir={{0,1},{0,-1},{-1,0},{1,0}}; vector<string>move={"R","L","U","D"}; dfs(0,0,m,curr,visited,dir,move,ans); return ans; }

};

Answer 1

Change

if (visited[nx][ny]==0 and m[nx][ny]==1 and nx>=0 and nx<m.size() and ny>=0 and ny<m.size()) {

to

if (nx>=0 and nx<m.size() and ny>=0 and ny<m.size() and visited[nx][ny]==0 and m[nx][ny]==1) {

You should only check visited and m after you have checked that nx and ny are in bounds. The order of the two sides of an and expression matters.

Answer 2

visited[nx][ny] == 0 is out-of-bounds. m[nx][ny] == 1 is out-of-bounds too.