如何使用C中的向量使用c的循環

使用C 中的for循環遍歷vector有多種方法，最常用的是C 11引入的基於範圍的for循環，它簡潔且安全，適用於只需訪問每個元素的場景；當需要元素索引時，應使用傳統的帶索引的for循環，通過size()和下標操作訪問元素；若需要更高靈活性（如配合STL算法或進行插入刪除操作），推薦使用迭代器遍歷，包括正向和反向迭代；此外，使用auto關鍵字可簡化代碼並提高可維護性，而選擇合適的方法取決於具體需求，例如是否需修改元素、是否僅讀取、是否需要索引或反向遍歷等，其中基於範圍的for循環在大多數情況下是首選方案。

Using a for loop with a vector in C is a common task, and there are several ways to do it depending on what you want to achieve. Here are the most practical and widely used approaches:

1. Range-based for loop (C 11 and later)

This is the simplest and safest way to iterate through all elements of a vector.

 #include <iostream>
#include <vector>
using namespace std;

int main() {
    vector<int> numbers = {10, 20, 30, 40, 50};

    for (int value : numbers) {
        cout << value << " ";
    }
    cout << endl;

    return 0;
}

• Use const int& if you don't want to copy large objects (eg, strings or custom objects):

   for (const auto& item : numbers) {
      cout << item << " ";
  }

• auto can also be used to avoid specifying the type:

   for (const auto& item : numbers)

2. Traditional for loop with index

Use this when you need the index of each element.

 vector<int> numbers = {10, 20, 30, 40, 50};

for (size_t i = 0; i < numbers.size(); i) {
    cout << "Index " << i << ": " << numbers[i] << endl;
}

• size_t is an unsigned type commonly used for sizes and indices.
• You can access and modify elements using numbers[i] .

3. Using iterators

This method gives you more control and is useful in algorithms or when working with parts of the vector.

 vector<int> numbers = {10, 20, 30, 40, 50};

for (auto it = numbers.begin(); it != numbers.end(); it) {
    cout << *it << " ";
}

• begin() returns an iterator to the first element.
• end() returns an iterator to one past the last element.
• Use *it to access the value.

You can also use const_iterator if you're only reading:

 for (auto it = numbers.cbegin(); it != numbers.cend(); it) {
    cout << *it << " ";
}

4. Reverse iteration

To loop from the end to the beginning:

 for (auto it = numbers.rbegin(); it != numbers.rend(); it) {
    cout << *it << " ";
}

• rbegin() points to the last element.
• rend() points before the first element.

Key Tips

• Prefer range-based for loops when you just need to process each element.
• Use index-based loops when you need the position.
• Use iterators when you need flexibility (eg, inserting, erasing, or passing to STL functions).
• Always be cautious with signed/unsigned comparisons (eg, don't compare int i with numbers.size() without casting).
• Use auto to reduce verbosity and improve maintainability.

Basically, pick the loop style that fits your needs. For most cases, the range-based for loop is clean and effective.

以上是如何使用C中的向量使用c的循環的詳細內容。更多資訊請關注PHP中文網其他相關文章！