問題描述

我有一個 std::vector m_vPaths;我將迭代這個向量并隨時調用 ::DeleteFile(strPath) .如果我成功刪除了文件，我會將其從向量中刪除.我的問題是我可以避免使用兩個向量嗎?是否有不同的數據結構可能更適合我需要做的事情?

I have a std::vector m_vPaths; I will iterate this vector and call ::DeleteFile(strPath) as I go. If I successfully delete the file, I will remove it from the vector. My question is can I get around having to use two vectors? Is there different data structure that might be better suited for what I need to do?

示例:使用迭代器幾乎可以滿足我的要求，但問題是一旦使用迭代器擦除，所有迭代器都將無效.

example: using iterators almost does what I want, but problem is once you erase using an iterator, all iterators become invalid.

 std::vector<std::string> iter = m_vPaths.begin();
    for( ; iter != m_vPaths.end(); iter++) {
        std::string strPath = *iter;
        if(::DeleteFile(strPath.c_str())) {
            m_vPaths.erase(iter);   
                //Now my interators are invalid because I used erase,
                //but I want to continue deleteing the files remaining in my vector.    
        }
    }

我可以使用兩個向量并且不再有問題，但是有沒有更好、更有效的方法來做我想做的事情?

I can use two vectors and I will no longer have a problem, but is there a better, more efficient method of doing what I'm trying to do?

順便說一句，如果不清楚，m_vPaths 是這樣聲明的(在我的班級中):

btw, incase it is unclear, m_vPaths is declared like this (in my class):

std::vector<std::string> m_vPaths;

推薦答案

查看 std::remove_if:

#include <algorithm> // for remove_if
#include <functional> // for unary_function

struct delete_file : public std::unary_function<const std::string&, bool> 
{
    bool operator()(const std::string& strPath) const
    {
        return ::DeleteFile(strPath.c_str());
    }
}

m_vPaths.erase(std::remove_if(m_vPaths.begin(), m_vPaths.end(), delete_file()),
                m_vPaths.end());

使用 std::list停止無效迭代器問題，盡管您失去了隨機訪問.(和緩存性能，一般)

Use a std::list to stop the invalid iterators problem, though you lose random access. (And cache performance, in general)

為了記錄，您實現代碼的方式是:

For the record, the way you would implement your code would be:

typedef std::vector<std::string> string_vector;
typedef std::vector<std::string>::iterator string_vector_iterator;

string_vector_iterator iter = m_vPaths.begin();
while (iter != m_vPaths.end())
{
    if(::DeleteFile(iter->c_str()))
    {
        // erase returns the new iterator
        iter = m_vPaths.erase(iter);
    }
    else
    {
        ++iter;
    }
}

但是你應該使用 std::remove_if(重新發明輪子不好).

But you should use std::remove_if (reinventing the wheel is bad).

這篇關于迭代向量，邊走邊刪除某些項目的文章就介紹到這了，希望我們推薦的答案對大家有所幫助，也希望大家多多支持html5模板網！