之前有个电话面试,其中一道题就是:用非递归的方式实现文件夹遍历?在电面的时候没有答出来,过后分分钟就想到了答案,因为之前自己实现过按层序的方式打印一棵树,用的也是非递归的方式,现在遍历文件夹不就是遍历这颗树吗!怎么就没想出来呢!在这里简单的记录下,用了C#和C++两个版本实现。
我这里的实现的功能是:用非递归的方式获得一个文件夹中文件的个数。
思路简单介绍:
1:先将这个文件夹的路径加入一个队列中;
2:判断队列的元素个数是否大于0,如果元素个数大于0,遍历第一个元素对应的文件夹,用一个变量fileCounts记录这个文件夹中文件的个数,如果这个文件夹中有文件夹,就将这个文件夹的路径加入队列中,扫描完一个文件夹后,第一个元素弹出队列,继续执行第二步,如果队列中没有元素,就执行第三步;
3:退出循环
C++版如下:
#include "stdafx.h" #include <Windows.h> #include <iostream> #include <queue> using namespace std; int QueryFileCounts( LPCTSTR Path ) { queue<std::wstring> qFolders; qFolders.push(Path); int fileCounts = 0; WIN32_FIND_DATA findResult; HANDLE handle=NULL; while(qFolders.size()>0) { std::wstring tempFolder = qFolders.front(); tempFolder.append(L"\\*.*"); handle = FindFirstFile(tempFolder.c_str(), &findResult); do { if (findResult.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) { if (lstrcmp(L".",findResult.cFileName)==0 || lstrcmp(L"..",findResult.cFileName)==0) { continue; } tempFolder=qFolders.front(); tempFolder.append(L"\\").append(findResult.cFileName); qFolders.push(tempFolder); }else{ fileCounts++; } } while (FindNextFile(handle, &findResult)); qFolders.pop(); } if (handle) { FindClose(handle); handle = NULL; } return fileCounts; } int _tmain(int argc, _TCHAR* argv[]) { { cout<< "文件个数:"<<QueryFileCounts(L"D:\\feinno\\RunImage")<<endl; } system("pause"); return 0; }
运行结果如下:
C#版代码如下:
using System; using System.Collections.Generic; namespace FileFind { class Program { [Serializable, System.Runtime.InteropServices.StructLayout(System.Runtime.InteropServices.LayoutKind.Sequential, CharSet = System.Runtime.InteropServices.CharSet.Auto),System.Runtime.InteropServices.BestFitMapping(false)] private struct WIN32_FIND_DATA { public int dwFileAttributes; public int ftCreationTime_dwLowDateTime; public int ftCreationTime_dwHighDateTime; public int ftLastAccessTime_dwLowDateTime; public int ftLastAccessTime_dwHighDateTime; public int ftLastWriteTime_dwLowDateTime; public int ftLastWriteTime_dwHighDateTime; public int nFileSizeHigh; public int nFileSizeLow; public int dwReserved0; public int dwReserved1; [System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValTStr,SizeConst = 260)] public string cFileName; [System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValTStr,SizeConst = 14)] public string cAlternateFileName; } [System.Runtime.InteropServices.DllImport("kernel32.dll", CharSet = System.Runtime.InteropServices.CharSet.Auto, SetLastError = true)] private static extern IntPtr FindFirstFile(string pFileName, ref WIN32_FIND_DATA pFindFileData); [System.Runtime.InteropServices.DllImport("kernel32.dll",CharSet = System.Runtime.InteropServices.CharSet.Auto,SetLastError = true)] private static extern bool FindNextFile(IntPtr hndFindFile, ref WIN32_FIND_DATA lpFindFileData); [System.Runtime.InteropServices.DllImport("kernel32.dll", SetLastError = true)] private static extern bool FindClose(IntPtr hndFindFile); static int QueryFileCounts( string Path ) { Queue<string> qFolders=new Queue<string>(); qFolders.Enqueue(Path); IntPtr INVALID_HANDLE_VALUE = new IntPtr(-1); int fileCounts = 0; WIN32_FIND_DATA FindFileData=new WIN32_FIND_DATA(); System.IntPtr hFind=INVALID_HANDLE_VALUE; while(qFolders.Count>0) { string floder=qFolders.Dequeue(); string tempFolder = floder; tempFolder+="\\*.*"; hFind = FindFirstFile(tempFolder ,ref FindFileData); if (hFind == INVALID_HANDLE_VALUE) { continue; } do { if ((FindFileData.dwFileAttributes & 0x10) != 0) { if (FindFileData.cFileName.Equals(".") || FindFileData.cFileName.Equals("..")) { continue; } tempFolder=floder+"\\"+FindFileData.cFileName; qFolders.Enqueue(tempFolder); }else{ fileCounts++; } } while (FindNextFile(hFind,ref FindFileData)); } if (hFind != INVALID_HANDLE_VALUE) { FindClose(hFind); } return fileCounts; } static void Main(string[] args) { int count=QueryFileCounts(@"D:\\feinno\\RunImage"); Console.WriteLine("文件个数:" + count ); Console.Read(); } } }
运行结果如下: