返回[_First,_Last)区间中第一个元素值等于val的元素位置

返回[_First,_Last)区间中第一个造成_Pred(elem)为true的元素

返回[_First,_Last)区间中第一个造成_Pred(elem)为false的元素

如果没有找到，都返回end

如果是已排序区间，应该使用lower_bound()、upper_bound()、equal_range()算法获得更高效能

Associative和unordered容器提供一个等效成员函数find（）拥有更好的复杂度

复杂度:线性

辅助函数：

template<typename T>
inline void INSERT_ELEMENTS(T& coll, int first, int last)
{for (int i = first; i <= last; ++i){coll.insert(coll.end(), i);}
}
template<typename T>
inline void PRINT_ELEMENTS(const T & coll, const string& optcstr = "")
{cout << optcstr;for (auto elem : coll){cout << elem << ' ';}cout << endl;}
template<typename T>
inline void PRINT_MAPPED_ELEMENTS(const T & coll, string& optcstr = "")
{cout << optcstr;for (auto elem : coll){cout << '[' << elem.first << ',' << elem.second << "] ";}cout << endl;
}

find()使用例子:

int main()
{list<int>coll;INSERT_ELEMENTS(coll, 1, 9);INSERT_ELEMENTS(coll, 1, 9);PRINT_ELEMENTS(coll, "coll: ");list<int>::iterator pos1;pos1 = find(coll.begin(), coll.end(), 4);list<int>::iterator pos2;if (pos1 != coll.end()){pos2 = find(++pos1, coll.end(), 4);}if (pos1 != coll.end() && pos2 != coll.end()){copy(--pos1, ++pos2, ostream_iterator<int>(cout, " "));cout << endl;}}

find_if()和find_if_not()例子:

int main()
{vector<int>coll;vector<int>::iterator pos;INSERT_ELEMENTS(coll, 1, 9);PRINT_ELEMENTS(coll, "coll: ");pos = find_if(coll.begin(), coll.end(), bind(greater<int>(), _1, 3));cout << "the " << distance(coll.begin(), pos) + 1 << ". element is the first greater than 3" << endl;pos = find_if(coll.begin(), coll.end(), [](int elem) {return elem % 3 == 0;});cout << "the " << distance(coll.begin(), pos) + 1 << ". element is the first divisible by 3" << endl;pos = find_if_not(coll.begin(), coll.end(), bind(less<int>(), _1, 5));cout << "first value >= 5: " << *pos << endl;}