Graph Ordering

input/code.cpp: In function 'int dis(int, std::vector<int>&)':
input/code.cpp:26:10: warning: 'max' may be used uninitialized in this function [-Wmaybe-uninitialized]
   return max;
          ^~~

#include <bits/stdc++.h>

using namespace std;

int n, m;
std::vector<std::vector<int> > e;

int dis(int f, std::vector<int> &df){
  deque<pair<int, int> > dq;
  dq.push_back({f, 0});
  std::vector<char> ma(n, 0);
  int max;
  while(!dq.empty()){
    int a, d;
    tie(a, d)=dq.front();
    dq.pop_front();
    if(ma[a])
      continue;
    ma[a]=1;
    df[a]=d;
    max=d;
    for(int &x: e[a])
      if(!ma[x])
        dq.push_back({x, d+1});
  }
  return max;
}

int main(){
  cin >> n >> m;
  e.resize(n);
  int a, b;
  for(int i=0; i<m; i++){
    cin >> a >> b;
    a--;
    b--;
    e[a].push_back(b);
    e[b].push_back(a);
  }
  if(n==m+1){
    for(int i=0; i<n; i++)
      if(e[i].size()>2){
        cout << "IMPOSSIBLE" <<endl;
        return 0;
      }
    int j=-1;
    for(int i=0; i<n; i++)
      if(e[i].size()==1){
        for(int k=0; k<n; k++){
          cout << i+1 <<" ";
          for(int &x: e[i])
            if(x!=j){
              j=i;
              i=x;
              break;
            }
        }
        cout << endl;
        return 0;
      }
  }
  for(int first=0; first<n; first++)
    for(int last=first+1; last<n; last++){
      std::vector<int> df (n, -1);
      std::vector<int> dl (n, -1);
      std::vector<int> out;
      std::vector<int> tim (n);
  int max=dis(first, df);
  dis(last, dl);
//  for(int i=0; i<n; i++)
  //  cout << df[i] << " "<<dl[i]<<endl;
  for(int i=0; i<=max; i++){
    std::vector<pair<int, int> > so;
    for(int j=0; j<n; j++)
      if(df[j]==i)
        so.push_back({-dl[j], j});
    sort(so.begin(), so.end());
    for(auto &x: so){
      tim[x.second]=out.size();
      out.push_back(x.second);
    }
  }
  deque<int> dq;
  dq.push_back(last);
  std::vector<char> ma(n, 0);
  while(!dq.empty()){
    int a=dq.front();
    dq.pop_front();
    if(ma[a])
      continue;
    ma[a]=1;
    for(int &x: e[a])
      if(!ma[x] && tim[a]>tim[x])
        dq.push_back(x);
  }
  int p=1;
  for(auto &x:ma)
    if(x==0){
      p=0;
      break;
    }
  if(!p)
    continue;
  //cout << ma[10000000]<<endl;
  for(int &x:out)
    cout << x+1<<" ";
  cout << endl;
  return 0;
}
cout << "IMPOSSIBLE"<<endl;
}

Test 1

Group: 1, 4, 5

Verdict: ACCEPTED

Test 2

Group: 1, 5

Verdict: ACCEPTED

Test 3

Group: 1, 5

Verdict: ACCEPTED

Test 4

Group: 1, 5

Verdict: ACCEPTED

Test 5

Group: 1, 5

Verdict: ACCEPTED

Test 6

Group: 2, 3, 5

Verdict: ACCEPTED

Test 7

Group: 2, 3, 5

Verdict: ACCEPTED

Test 8

Group: 2, 3, 4, 5

Verdict: WRONG ANSWER

Test 9

Group: 2, 3, 4, 5

Verdict: WRONG ANSWER

Test 10

Group: 2, 3, 4, 5

Verdict: WRONG ANSWER

Test 11

Group: 2, 3, 5

Verdict: WRONG ANSWER

Test 12

Group: 2, 3, 5

Verdict: WRONG ANSWER

Test 13

Group: 2, 3, 4, 5

Verdict: WRONG ANSWER

Test 14

Group: 2, 3, 4, 5

Verdict: WRONG ANSWER

Test 15

Group: 2, 3, 4, 5

Verdict: WRONG ANSWER

Test 16

Group: 2, 3, 4, 5

Verdict: WRONG ANSWER

Test 17

Group: 2, 3, 4, 5

Verdict: WRONG ANSWER

Test 18

Group: 2, 3, 4, 5

Verdict: WRONG ANSWER

Test 19

Group: 3, 4, 5

Verdict: TIME LIMIT EXCEEDED

Test 20

Group: 3, 4, 5

Verdict: TIME LIMIT EXCEEDED

Test 21

Group: 3, 4, 5

Verdict: TIME LIMIT EXCEEDED

Test 22

Group: 3, 4, 5

Verdict: TIME LIMIT EXCEEDED

Test 23

Group: 3, 5

Verdict: TIME LIMIT EXCEEDED

Test 24

Group: 3, 5

Verdict: TIME LIMIT EXCEEDED

Test 25

Group: 3, 5

Verdict: TIME LIMIT EXCEEDED

Test 26

Group: 3, 5

Verdict: TIME LIMIT EXCEEDED

Test 27

Group: 3, 5

Verdict: TIME LIMIT EXCEEDED

Test 28

Group: 5

Verdict: TIME LIMIT EXCEEDED

Test 29

Group: 5

Verdict: TIME LIMIT EXCEEDED

Test 30

Group: 4, 5

Verdict: TIME LIMIT EXCEEDED

Test 31

Group: 4, 5

Verdict: TIME LIMIT EXCEEDED

Test 32

Group: 4, 5

Verdict: TIME LIMIT EXCEEDED

Test 33

Group: 4, 5

Verdict: TIME LIMIT EXCEEDED

Test 34

Group: 5

Verdict: TIME LIMIT EXCEEDED

Test 35

Group: 5

Verdict: TIME LIMIT EXCEEDED

Test 36

Group: 5

Verdict: TIME LIMIT EXCEEDED

Test 37

Group: 1, 2, 3, 4, 5

Verdict: ACCEPTED

Test 38

Group: 2, 3, 5

Verdict: ACCEPTED

Test 39

Group: 2, 3, 5

Verdict: ACCEPTED

Test 40

Group: 2, 3, 5

Verdict: ACCEPTED

Test 41

Group: 1, 2, 3, 5

Verdict: ACCEPTED

Test 42

Group: 2, 3, 5

Verdict: ACCEPTED

Test 43

Group: 3, 4, 5

Verdict: TIME LIMIT EXCEEDED

Test 44

Group: 3, 4, 5

Verdict: TIME LIMIT EXCEEDED

Test 45

Group: 2, 3, 4, 5

Verdict: WRONG ANSWER

Test 46

Group: 2, 3, 4, 5

Verdict: WRONG ANSWER

Test 47

Group: 2, 3, 5

Verdict: WRONG ANSWER

Test 48

Group: 3, 4, 5

Verdict: TIME LIMIT EXCEEDED

Test 49

Group: 4, 5

Verdict: TIME LIMIT EXCEEDED