Declaration inside a loop

Question

In for loop like below

for(int i=0; i<n; i++) {
  vector<int>v(100);
}

In this i have a doubt that

1. for each loop will the vector will be declare again and again? If yes why it do not causes problem(because if we redeclare same thing it cause problem like two time int x;).

2. do the size keep on increasing on each loop till the end, in above or for such loop

for(int i=0;i<10000;i++) {
 int k;
}

Answer 1

for each loop will the vector will be declare again and again?

No.

There is only declaration but the object is constructed in each iteration of the loop and destructed in each iteration of the loop.

The following is illegal because there are two declaration of the variable.

for(int i=0;i<n;i++)
{
   vector<int> v(100);
   vector<int> v;
}

do the size keep on increasing on each loop till the end, in above or for such loop

It's not clear what you mean by that. Whose size are you talking about?

The size of the code generated by the compiler? That does not change.

The size of memory used by the computer at run time? That does not change either.

Does it take longer to run? Yes.