C Vector Erase Remove

2 removes the elements in the range first last.

C vector erase remove. Erase causes large amount of copies while remove just does a logical delete and leaves vector unchanged by moving element around. All the elements of the vector are removed using clear function. Another solution is to use std remove if with vector erase as shown below. C container from which to erase value value to be removed pred unary predicate which returns true if the element should be erased.

Erase function on the other hand is used to remove specific elements from the container or a range of elements from the container thus reducing its size by the number of elements removed. Notice that std remove if algorithm have no knowledge of the underlying container it does not actually remove elements from the container but move all safe elements to the front and returns an iterator pointing to where the end should be so. See this erasing elements from vector for more details. You need to use std remove algorithm to move the element to be erased to the end of the vector and then use erase function.

Here s how to do it. The combination of std remove and std erase allows you to remove matching elements from the container so that container would actually get truncated if elements were removed. This effectively reduces the container size by the number of elements removed which are destroyed. Myvector erase std remove myvector begin myvector end 8 myvec end.

The iterator pos must be valid and dereferenceable. The expression pred v must be convertible to bool for every argument v of type possibly const t regardless of value category and must not modify v thus a parameter type of t is not allowed nor is t unless for t a move is equivalent to a copy since. Because vectors use an array as their underlying storage erasing elements in positions other than the vector end causes the container to relocate all the elements after the segment erased to their new positions. Then you would remove 2 and shift all remaining elements by one 3 if you see the pattern this is a o n 2 algorithm.

Invalidates iterators and references at or after the point of the erase including the end iterator. Using erase if you went over the vector removing elements one by one you would remove the 1 causing copies of the remainder elements that get shifted 4. You can not do that directly. 1 3 4 5 2.

Now truncate the vector vec erase removed. Removes from the vector either a single element position or a range of elements first last.