我想做一个函数,如果项目符合某个条件,就把它们从一个STL列表移动到另一个列表。
这段代码不是做这件事的方法。迭代器很可能会被erase()函数失效,并导致问题:
for(std::list<MyClass>::iterator it = myList.begin(); it != myList.end(); it++)
{
if(myCondition(*it))
{
myOtherList.push_back(*it);
myList.erase(it);
}
}
那么,有没有人能推荐一种更好的方法呢?
发布于 2009-02-02 01:22:24
Erase
returns an iterator指向被擦除的元素之后的元素:
std::list<MyClass>::iterator it = myList.begin();
while (it != myList.end())
{
if(myCondition(*it))
{
myOtherList.push_back(*it);
it = myList.erase(it);
}
else
{
++it;
}
}
发布于 2009-03-05 14:00:38
std::list<MyClass>::iterator endMatching =
partition(myList.begin(), myList.end(), myCondition);
myOtherList.splice(myOtherList.begin(), myList, endMatching, myList.end());
请注意,partition()为您提供了足够的能力来区分匹配对象和非匹配对象。(list::splice()很便宜)
在一个受Now to remove elements that match a predicate?启发的具体案例中,请参阅以下代码
#include <iostream>
#include <iterator>
#include <list>
#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()
{
list<string> Strings;
Strings.push_back("213");
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");
// Linear. Exactly last - first applications of pred, and at most (last - first)/2 swaps.
list<string>::iterator end1 =
partition(Strings.begin(), Strings.end(), Pred);
list<string> NotMatching;
// This function is constant time.
NotMatching.splice(NotMatching.begin(),Strings, Strings.begin(), end1);
cout << "Elements matching with 1" << endl;
copy(Strings.begin(), Strings.end(), ostream_iterator<string>(cout,"\n"));
cout << "Elements not matching with 1" << endl;
copy(NotMatching.begin(), NotMatching.end(), ostream_iterator<string>(cout,"\n"));
return 0;
}
发布于 2009-02-02 01:19:55
另一次尝试:
for(std::list<MyClass>::iterator it = myList.begin(); it != myList.end; ) {
std::list<MyClass>::iterator eraseiter = it;
++it;
if(myCondition(*eraseiter)) {
myOtherList.push_back(*eraseiter);
myList.erase(eraseiter);
}
}
https://stackoverflow.com/questions/501962
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