segmentation fault

//#define NDEBUG
#define INF numeric_limits<int>::max()

#include <limits>
#include <string>
#include <queue>
#include <math.h>
#include <iostream>
#include <vector>
#include <algorithm>
#include <sstream>
#include <fstream>
#include <assert.h>
#include <set>
#include <map>
#include <cstdio>

using namespace std;

typedef long long int ll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<string> vs;
typedef vector<char> vc;
typedef pair<int,int> ii;
typedef pair<string,string> ss;
typedef vector<ii> vii;
typedef double db;
typedef vector<db> vdb;
typedef pair<db, db> dbdb;

int dijkstra(vector<vi> M) {
  priority_queue<pair<int, ii> > exploring; //weight, i, j.
  vector<vector<ii> > parents(M.size(), vector<ii>(M[0].size(), ii(-1,-1)));
  vector<vi> d(M.size(), vi(M[0].size(), INF));
  
  parents[0][0]=ii(-1,-1);
  d[0][0]=0;
  exploring.push(pair<int,ii>(0, ii(0,0)));

  while(!exploring.empty()) {
    ii explore = exploring.top().second; //i, j
    int weight = exploring.top().first;
    exploring.pop();
    
    if(weight > d[explore.first][explore.second])
      continue;


    int fi=explore.first, fj=explore.second, si, sj;
    cout << "on: " << fi << "," << fj << endl;
    for(int di=-1; di<2; di++) {
      for(int dj=-1; dj<2; dj++) {
	si = fi+di;
	sj = fj+dj;
	cout << "ding!" << endl;

	if(si>0 && si<M.size() &&
	   sj>0 && sj<M[0].size()) {
	  cout << "\tis inside the boundaries" << endl;
	  cout << di << "," << dj << endl;
	  if(abs(di) != abs(dj)) {
	    cout << "\tand is not a diagonal..." << endl;
	    if(d[fi][fj] + M[si][sj] < d[si][sj])
	      cout << "\tit is better than the another!" << endl;
	  } else {
	    cout << "'twas a diagonal :(" << endl;
	  }
	} else {
	  cout << "not inside the boundaries" << endl; //won't print this: Segmentation fault
	}
	
	// if( si>0 && si<M.size() && 
	//     sj>0 && sj<M[0].size() && 
	//     (abs(di) != abs(dj)) &&
	//     (d[fi][fj] + M[si][sj] < d[si][sj]) ) {
	//   cout << "ding!" << endl;
	//   d[si][sj] = d[fi][fj];
	//   parents[si][sj] = ii(fi,fj);
	//   exploring.push(pair<int, ii>(d[si][sj], ii(si, sj)));
	// }
      }
    }

  }

  return d[M.size()][M[0].size()];

}

int main(){
  int tc;
  scanf("%d", &tc);

  while(tc--) {
    int n, m;
    scanf("%d %d", &n, &m);
    vector<vi> M(n, vi(m));
    
    for(int i=0; i<n; i++) {
      for(int j=0; j<m; j++) {
	scanf("%d", &M[i][j]);
	cout << M[i][j] << " ";
      }
      cout << endl;
    }

    printf("%d\n", dijkstra(M));
  }

  
  return 0;
}