Why doesn't C++ take care of iterators when insertion is done in a vector after capacity is reached?

I wrote this small code just to see how an iterator actually gets invalidated and does not point to changed location of a vector after its capacity is reached. Here the size of vector and capacity is both 5 initially . After that I inserted a few other elements in vector and does not re-initialize my iterator to point to `myvector.begin()`. This lead to a junk value of `49` in my output after `maximum size of vector is : 1073741823` when printing elements of vector again. My question is why C++ does not make point iterator again to a valid `myvector.begin()` after all elements are copied into new location? This can also lead to some behavior which can be hard to debug. I know a safe way to work would be to always reinitialize the iterator just before using it. ``` #include<iostream> #include<vector> #include<stdio.h> using namespace std; int main() { vector<int> myvector; vector<int>::iterator it; int myarray[]= {100,200,300,400}; myvector.insert(it,500); it=myvector.begin(); myvector.insert(it,myarray,myarray+4); it=myvector.begin(); for(;it!=myvector.end();++it) cout <<*it<<endl; cout <<"size of vector is :" << myvector.size() <<"\n"; cout <<"capacity of vector is : " << myvector.capacity()<<"\n"; cout <<"maximum size of vector is : " << myvector.max_size()<<"\n"; myvector.push_back(600); for(;it!=myvector.end();++it) cout <<*it<<endl; } Output of program :- 100 200 300 400 500 size of vector is :5 capacity of vector is : 5 maximum size of vector is : 1073741823 49 100 200 300 400 500 600 ```