This question already has an answer here:
vector<int> myVector;
and lets say the values in the vector are this (in this order):
5 9 2 8 0 7
If I wanted to erase the element that contains the value of "8", I think I would do this:
myVector.erase(myVector.begin()+4);
Because that would erase the 4th element. But is there any way to erase an element based off of the value "8"? Like:
myVector.eraseElementWhoseValueIs(8);
Or do I simply just need to iterate through all the vector elements and test their values?
How about std::remove()
instead:
#include <algorithm>
...
vec.erase(std::remove(vec.begin(), vec.end(), 8), vec.end());
This combination is also known as the erase-remove idiom.
You can use std::find
to get an iterator to a value:
#include <algorithm>
std::vector<int>::iterator position = std::find(myVector.begin(), myVector.end(), 8);
if (position != myVector.end()) // == myVector.end() means the element was not found
myVector.erase(position);
You can not do that directly. 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.end(), 8), myVec.end());
. See this erasing elements from vector for more details.
Eric Niebler is working on a range-proposal and some of the examples show how to remove certain elements. Removing 8. Does create a new vector.
#include <iostream>
#include <range/v3/all.hpp>
int main(int argc, char const *argv[])
{
std::vector<int> vi{2,4,6,8,10};
for (auto& i : vi) {
std::cout << i << std::endl;
}
std::cout << "-----" << std::endl;
std::vector<int> vim = vi | ranges::view::remove_if([](int i){return i == 8;});
for (auto& i : vim) {
std::cout << i << std::endl;
}
return 0;
}
outputs
2
4
6
8
10
-----
2
4
6
10
来源:https://stackoverflow.com/questions/3385229/c-erase-vector-element-by-value-rather-than-by-position