Question

I’m writing a little piece of code where I’ll have to insert values into a C++ STL vector at a certain place depending on values in the vector elements. I’m using the insert() function to accomplish this. I realize that when I want to add a new element to the end of the vector, I could simply use push_back(). But to keep my code looking nice, I’d like to exclusively use insert(), which takes as input the iterator pointing to the element after the desired insertion point and the value to be inserted. If the value of the iterator passed in as an argument is v.end(), where v is my vector, will this work the same as push_back()?

Thanks a lot!

Answer 1

a.push_back(x) is defined to have identical semantics to (void)a.insert(a.end(),x) for sequence containers that support it.

See table 68 in ISO/IEC 14882:2003 23.1.1/12 [lib.sequence.reqmts].

Regarding the running time of vector.push_back(x) vs. vector.insert(vector.end(), x) consider the emphasized part:

Table 68 lists sequence operations that are provided for some types of sequential containers but not others. An implementation shall provide these operations for all container types shown in the ‘‘container’’ column, and shall implement them so as to take amortized constant time.