Efficiency of using c ++ vector

1. The efficiency of the erase method in vector is very low. In order to maintain the continuity of elements in the vector in the memory space, after deleting an element, you need to move the elements following it forward one position in sequence, with the average complexity of o (n ). The implementation of erase in gcc under www.2cto.com is as follows: iterator erase (iteratorposition) {if (position + 1! = End () copy (position + 1, finish, position); // move the subsequent elements forward -- finish; destroy (finish ); // return position;} a global function for resource release. Solution: If you want to delete an element at the last position, you do not need to move other elements. You only need o (1) based on this idea, we can implement an efficient method of deleting elements in a vector for (int I = 0; I <vec. size ();) {if (some condition) {swap (vec [I], vec [vec. size ()-1]); vec. pop_back () ;}else {I ++ ;}} 2. the iterator uses vector <int> int_vec; for (vector <int>: iterator iter = int_vec.begin (); iter! = Int_vec.end (); ++ iter ){...} note that you must use ++ iter. You cannot use iter ++ to copy a value first, and then perform ++ with low efficiency.