05. 讀入/寫出 檔案

使用函式庫 "stdio.h" 中的函式 "freopen" (reopen stream with different files or modes)" 簡單的讀取文字檔案資料。

// 以下是在 C++ Builder 撰寫的範例

// "in.txt" 為 .txt 檔案，且須事先將 in.txt 檔案放在與 .exe 檔案相同的目錄，以下為 in.txt 檔內容：

//  5 6

//  0 0 0 0 0 0

//  0 1 1 1 1 0

//  0 1 1 1 1 0

//  0 1 1 1 1 0

//  0 0 0 0 0 0

#include <stdio.h>

#include <vcl.h>

#pragma hdrstop

#include "Unit1.h"

//---------------------------------------------------------------

#pragma package(smart_init)

#pragma resource "*.dfm"

using namespace std;   // Add this statement for using "cin"/"cout"

TForm1 *Form1;

//----------------------------------------------------------------

__fastcall TForm1::TForm1(TComponent* Owner): TForm(Owner)

{

}

//------------------------------------------------------------------

void __fastcall TForm1::Button1Click(TObject *Sender)

{   int m, n, i, j;

freopen("in.txt", "r", stdin); 

// read data in "in.txt" as standard input 將 in.txt 內容當成 stdin

freopen("out.txt", "w", stdout);  // 將輸出結果寫入 "out.txt" 檔案，會在與 .exe 相同之目錄生成 out.txt 檔案

cin >> m >> n; // 自 in.txt (stdin) 輸入矩陣大小

int ** maze;

maze = new int * [m];

     for (int i=0; i<m; i++)

     {    maze[i] = new int [n];

for (int j=0; j<n; j++)

          cin >> maze[i][j];  // 自 in.txt (stdin) 讀資料

     }

     fclose(stdin);

     cin.clear();

     String s;  // 將輸出寫入 Form1

for (int i=0; i<m; i++)

{     for (int j=0, s=""; j<n; j++)

s = s + IntToStr(maze[i][j]) + " ";

Form1->Memo1->Lines->Add(s);

}

// 將輸出寫入 out.txt 檔案

cout << m << " " << n << endl;

for (i=0; i<m; i++)

{      for (j=0; j<n; j++)

cout << maze[i][j] <<" ";

cout << endl;

}

fclose(stdout);

}

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• 讀入/寫出 檔案 (執行檔)

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將檔案內容(含兩整數m,n和 m*n 個整數)讀入程式中 (BCB)：

#include "stdio.h"

//---------------------------------------------------------------------------

#pragma package(smart_init)

#pragma resource "*.dfm"

TForm1 *Form1;

//---------------------------------------------------------------------------

__fastcall TForm1::TForm1(TComponent* Owner)

        : TForm(Owner)

{

}

//---------------------------------------------------------------------------

int maze [20][20];

void __fastcall TForm1::Button1Click(TObject *Sender)

{

  FILE *fp;

  AnsiString out, fname;

  int m, n, i, j;

  if (OpenDialog1->Execute())

  {   fname = OpenDialog1->FileName;

fp = fopen(fname.c_str(), "r+");  

      //c_str函数的傳回值是 const char *, 即把string轉成const char *

       fscanf(fp, "%d %d", &m, &n);    // Reda in two integers m & n

       Memo1->Lines->Add("m="+IntToStr(m));

       Memo1->Lines->Add("n="+IntToStr(n));

      for (i=1; i<=m; i++)      // Reda in m*n 0/1's into maze[][]

         for (j=1; j<=n; j++)

             fscanf(fp, "%d", &maze[i][j]);

     for (i=1; i<=m; i++)      // Print out maze[][] in Memo1

     {   out = "";

         for (j=1; j<=n; j++)

             out += "  "+IntToStr(maze[i][j]);

         Memo1->Lines->Add(out);

     }            

     // Print out maze[][] in StringGrid1

     StringGrid1->RowCount = m+1;

     StringGrid1->ColCount = n+1;

     for (i=1; i<=m; i++)

     {   for (j=1; j<=n; j++)

         {   StringGrid1->Cells[j-1][i-1] = maze[i][j];

         }

     }

     fclose(fp);

  }

  else  Memo1->Lines->Add("Nothing happens.");

 }

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4 4

0 1 1 0

0 0 1 1

1 0 0 1

1 1 1 0

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