223 lines
6.5 KiB
Markdown
223 lines
6.5 KiB
Markdown
以下是 C++ STL 中 `std::vector` 的**全面用法大全**（涵盖常用与高级功能，包含中英文注释，适合查阅与系统学习）：
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---
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## 🔷 `std::vector` 概述
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`std::vector` 是一个**动态数组容器**，支持快速的随机访问与末尾插入。
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```cpp
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#include <vector>
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using namespace std;
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vector<int> v; // 空 vector
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vector<int> v(5); // 5 个元素，值为 0
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vector<int> v(5, 10); // 5 个元素，值为 10
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vector<int> v2 = {1, 2, 3}; // 列表初始化
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vector<int> v3(v2); // 拷贝构造
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```
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---
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## 🧰 常用成员函数分类一览
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### ✅ 构造与初始化
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```cpp
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vector<int> v; // 默认构造
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vector<int> v(10); // 10个默认值元素（int 默认是0）
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vector<int> v(5, 3); // 5个3
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vector<int> v2 = {1, 2, 3}; // 初始化列表
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vector<int> v3(v2); // 拷贝构造
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v.assign(4, 100); // 用4个100赋值
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v.assign({1, 2, 3, 4}); // 用初始化列表赋值
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```
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---
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### ✅ 容量相关
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```cpp
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v.size(); // 元素个数
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v.capacity(); // 容量（预留空间）
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v.max_size(); // 最大可容纳元素数
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v.empty(); // 是否为空
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v.resize(10); // 调整为10个元素，默认填0
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v.resize(10, -1); // 用-1填充新元素
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v.shrink_to_fit(); // 缩容至实际大小
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v.reserve(100); // 提前分配至少100个容量
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```
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---
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### ✅ 元素访问
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```cpp
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v[0]; // 下标访问
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v.at(0); // 范围检查的访问，越界会抛异常
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v.front(); // 第一个元素
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v.back(); // 最后一个元素
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v.data(); // 返回底层数组指针（T* 类型）
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```
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---
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### ✅ 修改函数
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```cpp
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v.push_back(5); // 末尾添加
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v.pop_back(); // 移除末尾元素
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v.insert(v.begin(), 3); // 在开头插入3
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v.insert(v.begin() + 2, 4, 9); // 在第3个位置插入4个9
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v.insert(v.end(), {7, 8, 9}); // 插入初始化列表
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v.erase(v.begin()); // 删除第一个
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v.erase(v.begin(), v.begin()+3);// 删除前3个
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v.clear(); // 清空所有元素
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v.swap(v2); // 与另一个vector交换内容
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```
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---
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### ✅ 迭代器相关
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```cpp
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vector<int>::iterator it = v.begin(); // 正向迭代器
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vector<int>::iterator end = v.end();
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vector<int>::reverse_iterator rit = v.rbegin(); // 反向迭代器
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vector<int>::const_iterator cit = v.cbegin(); // 只读正向
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vector<int>::const_reverse_iterator crit = v.crbegin(); // 只读反向
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```
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---
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### ✅ 排序与查找（配合算法头 `<algorithm>`）
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```cpp
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#include <algorithm>
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sort(v.begin(), v.end()); // 升序
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sort(v.rbegin(), v.rend()); // 降序
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reverse(v.begin(), v.end()); // 翻转
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find(v.begin(), v.end(), 3); // 查找3
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count(v.begin(), v.end(), 3); // 统计3出现次数
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```
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---
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### ✅ 与其他容器函数通用的操作
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```cpp
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for (auto x : v) cout << x; // 范围for
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for (auto it = v.begin(); it != v.end(); ++it)
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cout << *it;
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```
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---
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### ✅ C++11\~20 新特性支持
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```cpp
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v.emplace_back(10); // 直接构造末尾元素
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v.emplace(v.begin(), 20); // 在指定位置构造
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```
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---
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## 📝 常见用途小例子
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### 1. 输入一串数字
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```cpp
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vector<int> v;
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int x;
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while (cin >> x) v.push_back(x);
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```
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### 2. 二维 vector
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```cpp
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vector<vector<int>> grid(5, vector<int>(10, 0)); // 5x10 矩阵
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```
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### 3. 排序 + 去重
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```cpp
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sort(v.begin(), v.end());
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v.erase(unique(v.begin(), v.end()), v.end());
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```
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---
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## 🧠 小总结
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| 分类 | 函数举例 |
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| ---------- | --------------------------------------------------- |
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| 初始化 | `vector<int> v(10, 5)` |
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| 容量操作 | `resize`, `reserve`, `shrink_to_fit` |
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| 元素访问 | `[]`, `at`, `front`, `back`, `data` |
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| 增删改 | `insert`, `erase`, `push_back`, `pop_back`, `clear` |
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| 迭代器 | `begin`, `end`, `rbegin`, `cbegin`, `crend` |
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| 算法配合 | `sort`, `find`, `reverse`, `unique` |
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| C++11/14特性 | `emplace`, `auto`, `range-for` |
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---
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如需我生成一份 `.cpp` 文件、或你希望看到某种使用场景的完整案例，比如：
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* 大量数据插入性能优化
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* 模拟二维表格
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* 搜索 + 删除特定值
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* 用 `vector` 实现栈/队列
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我可以为你分别写出来。需要哪一种？
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Member functions
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(constructor) Construct vector (public member function)
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(destructor) Vector destructor (public member function)
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operator= Assign content (public member function)
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Iterators:
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begin Return iterator to beginning (public member function)
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end Return iterator to end (public member function)
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rbegin Return reverse iterator to reverse beginning (public member function)
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rend Return reverse iterator to reverse end (public member function)
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cbegin Return const_iterator to beginning (public member function)
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cend Return const_iterator to end (public member function)
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crbegin Return const_reverse_iterator to reverse beginning (public member function)
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crend Return const_reverse_iterator to reverse end (public member function)
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Capacity:
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size Return size (public member function)
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max_size Return maximum size (public member function)
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resize Change size (public member function)
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capacity Return size of allocated storage capacity (public member function)
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empty Test whether vector is empty (public member function)
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reserve Request a change in capacity (public member function)
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shrink_to_fit Shrink to fit (public member function)
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Element access:
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operator[] Access element (public member function)
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at Access element (public member function)
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front Access first element (public member function)
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back Access last element (public member function)
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data Access data (public member function)
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Modifiers:
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assign Assign vector content (public member function)
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push_back Add element at the end (public member function)
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pop_back Delete last element (public member function)
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insert Insert elements (public member function)
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erase Erase elements (public member function)
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swap Swap content (public member function)
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clear Clear content (public member function)
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emplace Construct and insert element (public member function)
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emplace_back Construct and insert element at the end (public member function)
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Allocator:
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get_allocator Get allocator (public member function)
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Non-member function overloads
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relational operators Relational operators for vector (function template)
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swap Exchange contents of vectors (function template) |