使用惰性迭代器的C++过滤

#include <iostream>
#include <vector>
#include <algorithm>

// 定义一个惰性迭代器
template<typename T, typename Predicate>
class LazyFilterIterator {
public:
    LazyFilterIterator(T begin, T end, Predicate predicate)
        : begin_(begin), end_(end), predicate_(predicate) {}

    // 重载迭代器操作符
    auto operator*() {
        return *current_;
    }

    // 重载递增操作符
    LazyFilterIterator& operator++() {
        ++current_;
        advanceToNextValidElement();
        return *this;
    }

    // 重载相等操作符
    bool operator==(const LazyFilterIterator& other) const {
        return current_ == other.current_;
    }

    // 重载不等操作符
    bool operator!=(const LazyFilterIterator& other) const {
        return !(*this == other);
    }

private:
    T begin_;
    T end_;
    Predicate predicate_;
    T current_;

    // 辅助函数，将迭代器移动到下一个符合条件的元素
    void advanceToNextValidElement() {
        while (current_ != end_ && !predicate_(*current_)) {
            ++current_;
        }
    }
};

// 辅助函数，用于创建惰性迭代器
template<typename T, typename Predicate>
auto make_lazy_filter_iterator(T begin, T end, Predicate predicate) {
    return LazyFilterIterator<T, Predicate>(begin, end, predicate);
}

int main() {
    std::vector<int> numbers = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

    // 使用惰性迭代器过滤出偶数
    auto evenNumbers = make_lazy_filter_iterator(numbers.begin(), numbers.end(), [](int num) {
        return num % 2 == 0;
    });

    // 遍历并输出过滤后的结果
    for (const auto& num : evenNumbers) {
        std::cout << num << " ";
    }
    std::cout << std::endl;

    return 0;
}