Remove ith item from a C++ std::vector [duplicate]

Question

How do I remove the ith item from a std::vector?

I know I want to delete the ith element. I have int i; and std::vector<process> pList; where process is a struct. I want to do something equivalent to the following:

pList.remove(i); 

Answer 1

pList.erase(pList.begin()+i); 

To remove element with index i.

Answer 2

Here is an O(1) solution, assuming you don't care about the order of elements:

#include <algorithm>  // ...  {     using std::swap;     swap(pList[i], pList.back());     pList.pop_back(); } 

For PODs, assignment is faster than swapping, so you should simply write:

pList[i] = pList.back(); pList.pop_back(); 

In C++11, you can forget the above distinction and always use move semantics for maximum efficiency:

if (i != pList.size() - 1) {     // Beware of move assignment to self     // see http://stackoverflow.com/questions/13127455/     pList[i] = std::move(pList.back()); } pList.pop_back();