Menu
I have a vector that will store a variable number of zero elements at its beginning. These need to be erased.
I have tried:
while(v.at(0) == 0)
{
v.erase(v.begin());
}
But this throws out an std::out_of_range error.
Any assistance would be appreciated.
851
asked Aug 13 '18 11:08
All the elements of the vector are removed using clear() function. 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.
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. Something like: myVector. erase(std::remove(myVector. begin(), myVector.
If you need to remove multiple elements from the vector, the std::remove will copy each, not removed element only once to its final location, while the vector::erase approach would move all of the elements from the position to the end multiple times.
Get the vector and the element to be deleted Initialize a reverse iterator on the vector Erase the required element with the help of base () and erase () Reason for using base (): erase () returns a valid iterator to the new location of the element which follows the one, which was just erased, in a forward sense.
What happens is that remove compacts the elements that differ from the value to be removed ( number_in) in the beginning of the vector and returns the iterator to the first element after that range. Then erase removes these elements (whose value is unspecified). Show activity on this post.
//Now the vector (v) has 2 elements in it, with size 2 v.pop_front(); // This method will remove the first element for(int i=0;i<v.size();i++){ cout << v[i] << " "; } //Prints [1] return 0; } Removes either a single element or a range of elements.
What happens is that remove compacts the elements that differ from the value to be removed ( number_in) in the beginning of the vector and returns the iterator to the first element after that range. Then erase removes these elements (whose value is unspecified). std::remove () shifts elements such that the elements to remove are overwritten.
You can use std::find_if to find the first non-zero value and then erase those elements:
auto first_non_zero = std::find_if(begin(v), end(v), [](int n){ return n != 0; });
v.erase(begin(v), first_non_zero);
(live demo)
175
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
