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PONow to remove elements that match a predicate?
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copied!<p>I have a source container of strings I want to remove any strings from the source container that match a predicate and add them into the destination container.</p> <p><code>remove_copy_if</code> and other algorithms can only reorder the elements in the container, and therefore have to be followed up by the <code>erase</code> member function. My book (Josuttis) says that <code>remove_copy_if</code> returns an iterator after the last position in the destination container. Therefore if I only have an iterator into the destination container, how can I call <code>erase</code> on the source container? I have tried using the size of the destination to determine how far back from the end of the source container to erase from, but had no luck. I have only come up with the following code, but it makes two calls (<code>remove_if</code> and <code>remove_copy_if</code>).</p> <p>Can someone let me know the correct way to do this? I'm sure that two linear calls is not the way to do this.</p> <pre><code>#include <iostream> #include <iterator> #include <vector> #include <string> #include <algorithm> #include <functional> using namespace std; class CPred : public unary_function<string, bool> { public: CPred(const string& arString) :mString(arString) { } bool operator()(const string& arString) const { return (arString.find(mString) == std::string::npos); } private: string mString; }; int main() { vector<string> Strings; vector<string> Container; Strings.push_back("123"); Strings.push_back("145"); Strings.push_back("ABC"); Strings.push_back("167"); Strings.push_back("DEF"); cout << "Original list" << endl; copy(Strings.begin(), Strings.end(),ostream_iterator<string>(cout,"\n")); CPred Pred("1"); remove_copy_if(Strings.begin(), Strings.end(), back_inserter(Container), Pred); Strings.erase(remove_if(Strings.begin(), Strings.end(), not1(Pred)), Strings.end()); cout << "Elements beginning with 1 removed" << endl; copy(Strings.begin(), Strings.end(),ostream_iterator<string>(cout,"\n")); cout << "Elements beginning with 1" << endl; copy(Container.begin(), Container.end(),ostream_iterator<string>(cout,"\n")); return 0; } </code></pre>

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