find_if

find_if的STL定义：template <class InputIterator, class Predicate>InputIterator find_if(InputIterator first, InputIterator last,Predicate pred){while (first != last && !pred(*first)) ++first;return first; //传入的是迭代器解引用后的}

//例子1
struct isWanted{
bool operator()(int a){
return  a==5;
}
};

int main(){
vector<int> vec;
vec.push_back(1);
vec.push_back(2);
vec.push_back(6);
vec.push_back(5);
vec.push_back(9);
vec.push_back(0);
vec.push_back(3);

vector<int>::iterator ans=find_if(vec.begin(),vec.end(),isWanted());
cout<<ans-vec.begin()<<endl;
return 0;
}