Alternative version of find_if which finds all, not just the first?

问题

Is there an alternative version of std::find_if that returns an iterator over all found elements, instead of just the first one?

Example:

bool IsOdd (int i) {
  return ((i % 2) == 1);
}

std::vector<int> v;
v.push_back(1);
v.push_back(2);
v.push_back(3);
v.push_back(4);

std::vector<int>::iterator it = find_if(v.begin(), v.end(), IsOdd);
for(; it != v.end(); ++it) {
  std::cout << "odd: " << *it << std::endl;
}

回答1:

You can just use a for loop:

for (std::vector<int>:iterator it = std::find_if(v.begin(), v.end(), IsOdd);
     it != v.end();
     it = std::find_if(++it, v.end(), IsOdd))
{
    // ...
}

Alternatively, you can put your condition and action into a functor (performing the action only if the condition is true) and just use std::foreach.

回答2:

in STL there isn't, but boost offers this funcionality:

boost::algorithm::find_all

回答3:

First always try to come up with typical STL usage itself, you can go for boost as well. Here is more simplified form from the above mentioned answer by Charles.

    vec_loc = find_if(v3.begin(), v3.end(), isOdd);
if (vec_loc != v3.end())
{
    cout << "odd elem. found at " << (vec_loc - v3.begin()) << "and elem found is " << *vec_loc << endl;
    ++vec_loc;
}
for (;vec_loc != v3.end();vec_loc++) 
{
    vec_loc = find_if(vec_loc, v3.end(), isOdd);
    if (vec_loc == v3.end())
        break;
    cout << "odd elem. found at " << (vec_loc - v3.begin()) << "and elem found is " << *vec_loc << endl;
}

来源：https://stackoverflow.com/questions/2344673/alternative-version-of-find-if-which-finds-all-not-just-the-first