Why does declaring vector inside of the loop result in TLE. Eg
Outside
vector<int> visited(n);
for(){
visited.assign(n, 0);
// other code;
}
Inside
for(){
vector<int> visited(n);
// other code;
}
In the problem below, the "outside" method is AC with 765ms, but the "inside" method is TLE at 3000ms.
Why? I can understand there must be some extra cost to re-allocate and de-allocate memory for the vector, but is the constant factor really that high? Time Complexity is the same (size of the vector), so I was quite surprised. Would be great if anyone can share more insights. Thanks!
Context: I was working Codeforces Round 938 (Div. 3), problem G: GCD on a grid.
Eg example accepted solution: https://codeforces.me/contest/1955/submission/260714562 vs TLE solution with declaration inside loop: 260714503 (recommend using CF compare)