> For the complete documentation index, see [llms.txt](https://docs.1l.lol/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.1l.lol/data-structures/stl.md).

# STL 标准库

### STL 是什么

STL（标准模板库）提供现成的**容器、迭代器和算法**，让编程更高效。需要 `#include` 对应头文件。

### 常用容器

| 容器               | 说明             | 头文件         |
| ---------------- | -------------- | ----------- |
| `vector`         | 动态数组           | `<vector>`  |
| `string`         | 字符串            | `<string>`  |
| `pair`           | 二元组            | `<utility>` |
| `set / multiset` | 有序集合（去重 / 不去重） | `<set>`     |
| `map`            | 键值映射（有序）       | `<map>`     |
| `stack`          | 栈              | `<stack>`   |
| `queue`          | 队列             | `<queue>`   |
| `priority_queue` | 优先队列（堆）        | `<queue>`   |
| `deque`          | 双端队列           | `<deque>`   |

```cpp
vector<int> v = {3, 1, 4};
v.push_back(2);              // 追加
cout << v.size();            // 元素个数
sort(v.begin(), v.end());    // 排序

map<string, int> mp;
mp["apple"] = 3;             // 键值对
cout << mp["apple"];         // 3
```

### 迭代器

迭代器是访问容器元素的“指针”：

```cpp
for (auto it = v.begin(); it != v.end(); ++it)
    cout << *it << " ";
for (int x : v) cout << x << " ";   // 范围 for，更简洁
```

### 常用算法（）

| 函数                           | 作用              |
| ---------------------------- | --------------- |
| `sort(begin, end)`           | 排序              |
| `reverse(begin, end)`        | 翻转              |
| `find(begin, end, x)`        | 查找              |
| `lower_bound(begin, end, x)` | 第一个 ≥ x 的位置（有序） |
| `upper_bound(begin, end, x)` | 第一个 > x 的位置（有序） |
| `max(a, b)` / `min(a, b)`    | 取最值             |
| `swap(a, b)`                 | 交换              |

### 小结

先掌握 `vector`、`string`、`pair`、`map`、`set` 和 `sort`，再学 `stack/queue/priority_queue`，是竞赛最常用的组合。


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