查看“︁09-进阶算法/06-重载运算符与迭代器”︁的源代码


== 重载运算符 ==

C++ 允许自定义类型的运算符行为，使结构体可以直接用 <code>+</code>、<code><</code>、<code><<</code> 等运算符操作。

=== 比较运算符 ===

用于 <code>sort</code> 或优先队列等场景：

<syntaxhighlight lang="cpp">
struct Student
{
    string name;
    int score, age;

    // 按分数降序，分数相同按年龄升序
    bool operator<(const Student& that) const
    {
        if (score != that.score)
            return score < that.score;
        return age < that.age;
    }
};

vector<Student> v;
sort(v.begin(), v.end()); // 按重载的 < 排序
</syntaxhighlight>

=== 算术运算符 ===

<syntaxhighlight lang="cpp">
struct Point
{
    int x, y;

    Point operator+(const Point& that) const
    {
        return {x + that.x, y + that.y};
    }

    Point operator-(const Point& that) const
    {
        return {x - that.x, y - that.y};
    }
};

Point a{1, 2}, b{3, 4};
Point c = a + b; // {4, 6}
</syntaxhighlight>

=== 输入输出运算符 ===

<syntaxhighlight lang="cpp">
struct Point
{
    int x, y;

    friend istream& operator>>(istream& in, Point& p)
    {
        return in >> p.x >> p.y;
    }

    friend ostream& operator<<(ostream& out, const Point& p)
    {
        return out << "(" << p.x << ", " << p.y << ")";
    }
};
</syntaxhighlight>

== 迭代器 ==

迭代器是访问容器元素的通用接口。

=== 常用迭代器操作 ===

<syntaxhighlight lang="cpp">
vector<int> v = {1, 2, 3, 4, 5};

vector<int>::iterator it;
for (it = v.begin(); it != v.end(); it++)
    cout << *it << " ";

// C++11 auto 简化
for (auto it = v.begin(); it != v.end(); it++)
    cout << *it << " ";

// 范围 for 循环
for (int x : v)
    cout << x << " ";
</syntaxhighlight>

=== 迭代器分类 ===

{| class="wikitable"
! 迭代器类型 !! 支持操作 !! 示例容器
|-
| 输入/输出迭代器
| 读取/写入、<code>++</code>
| <code>istream_iterator</code>
|-
| 前向迭代器
| 读取、写入、<code>++</code>
| <code>forward_list</code>
|-
| 双向迭代器
| 前向 + <code>--</code>
| <code>list</code>、<code>set</code>、<code>map</code>
|-
| 随机访问迭代器
| 双向 + <code>+n</code>、<code>[n]</code>
| <code>vector</code>、<code>deque</code>、<code>string</code>
|}

[[Category:进阶算法]]
[[Category:三三文档]]