Remove matched elements from 2 different vectors [duplicate]

Question

How can i remove matched elements in c++ while keeping the same order ? i found similar question here but they sort the elements while i want to keep the order for example i have v1{1,2,3,4} , v2{8,6,2,4,3} ,the result should be {1},{8,6}.

here is my code

#include <iostream> #include<vector> using namespace std; int main() { vector<int> v1{1,2,3,4},v2{8,2,4,3}; for (auto i=0;i<v1.size();i++){ for (auto j=0;j<v2.size();j++){ if (v1[i]==v2[j]) { v1.erase(v1.begin()+i); v2.erase(v2.begin()+j); } } } return 0; }

but it gives wrong result so how can i get it done?

removing elements does not alter order of remaning ones, hence the question is unclear — 463035818_is_not_an_ai
– 463035818_is_not_an_ai, Commented Nov 2, 2023 at 8:51
Your current code skips elements. If you sit down to think about it a little, perhaps using pen and paper to help, I'm sure you will figure out what's happening and why. — Some programmer dude
– Some programmer dude, Commented Nov 2, 2023 at 8:51
what is wrong results? You should include output and expected output in the question. This code has no ouput. Did you use a debugger? Please mention that in the question. — 463035818_is_not_an_ai
– 463035818_is_not_an_ai, Commented Nov 2, 2023 at 8:51
As for a simple way to solve your problem, I recommend you iterate using iterators and use what erase returns. — Some programmer dude
– Some programmer dude, Commented Nov 2, 2023 at 8:52
stackoverflow.com/a/8628963/4165552 - like this, but there will be 2 nested loops in your case — pptaszni
– pptaszni, Commented Nov 2, 2023 at 8:56

Pepijn Kramer · Accepted Answer · 2023-11-02 09:06:00Z

If you can avoid raw loops, like this

#include <algorithm> #include <iostream> #include <vector> int main() { std::vector<int> v1{1, 2, 3, 4}, v2{ 8,2,4,3,6 }; auto it1 = std::remove_if(v1.begin(), v1.end(), [&](const int value) { return (std::find(v2.begin(), v2.end(), value) != v2.end()); }); // don't erase just yet (elements to be deleted will be moved to end, the rest should have preserved their order) auto it2 = std::remove_if(v2.begin(), v2.end(), [&](const int value) { return (std::find(v1.begin(), v1.end(), value) != v1.end()); }); v1.erase(it1, v1.end()); v2.erase(it2, v2.end()); for (const int value : v1) std::cout << value << " "; std::cout << "\n"; for (const int value : v2) std::cout << value << " "; std::cout << "\n"; return 0; }

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