### Hello codeforces,

On this problem 1277E - Две ярмарки, there is *t* test cases and I am using a *vector<vector> ed(N)* to store the edges of the graph, so in end of each test case I need to clear my vector *ed* so I created another one *vector<vector> em(N)* and it's empty all the running time, in the end of each test case I did *ed = em* to save time, but I were always getting a TLE on the 2nd test, and I don't know why. In the first submission 68468115, I did

```
vector<vector<int> > ed(N), em(N);
int main() {
cin >> t;
while(t--){
...
...
...
ed = em;
}
return 0;
}
```

But when I did the following in this submission 68489443, I got an *AC*.

```
vector<vector<int> > ed(N);
int main() {
cin >> t;
while(t--){
...
...
...
for(int i=0; i<n; i++) ed[i].clear();
}
return 0;
}
```

**Can someone explain why I were getting a TLE on the first submission, even that in the first submission I were doing one operation but in the second one I were doing N operations.**