reading multidimensional array from a file

This is a discussion on reading multidimensional array from a file within the C++ Programming forums, part of the General Programming Boards category; Code: #include <iostream> #include <fstream> using namespace std; #define MAP_WIDTH 70 #define MAP_HEIGHT 22 void readMap(int map[MAP_WIDTH][MAP_HEIGHT]) { ifstream fin; ...

  1. #1
    Registered User abrege's Avatar
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    reading multidimensional array from a file

    Code:
    #include <iostream>
    #include <fstream>
    using namespace std;
    
    #define MAP_WIDTH 70
    #define MAP_HEIGHT 22
    
    void readMap(int map[MAP_WIDTH][MAP_HEIGHT])
    {
    	ifstream fin;
    	fin.open("test.txt");
    
    	for(int i = 0; i < MAP_WIDTH; i ++)
    	{
    		for(int t = 0; t < MAP_HEIGHT; t ++)
    			fin >> map[i][t];
    	}
    
    	fin.close();
    }
    
    void dispMap(int map[MAP_WIDTH][MAP_HEIGHT])
    {
    	for(int i = 0; i < MAP_WIDTH; i ++)
    	{
    		for(int t = 0; t < MAP_HEIGHT; t ++)
    		{
    			if(map[i][t] == 0)
    				cout << ' ';
    			else if(map[i][t] == 1)
    				cout << '.';
    			else if(map[i][t] == 2)
    				cout << '#';
    		}
    
    		cout << endl;
    	}
    }
    
    int main()
    {
    	int map[MAP_WIDTH][MAP_HEIGHT];
    
    	readMap(map);
    	dispMap(map);
    
    	return 0;
    }
    When I run this program all that shows up are many blank lines. Any help would be appreciated.
    Attached Files Attached Files
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  2. #2
    and the hat of wrongness Salem's Avatar
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    You need to read the file as chars rather than ints, and convert each char to an int yourself

    At present, each row is taken as being just one int, either zero with lots of leading zeros, or something rather large, with lots of leading zeros.
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  3. #3
    Carnivore ('-'v) Hunter2's Avatar
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    You could also put spaces between each character, I think.
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  4. #4
    Registered User eth0's Avatar
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    Does a multidimensional array not read accross and then skip down a line?
    If so I think your loops are back to front. Should the height not be specified first and then traverse the inner loop along the width???
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  5. #5
    and the hat of wrongness Salem's Avatar
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    Good call eth0!
    The map itself is also wrong then, it should be
    int map[MAP_HEIGHT][MAP_WIDTH];
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  6. #6
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    Oh, I'm interested in your programme, too. Would you please post the finally version of your programming source code here, thx.

    By the way, would you mind writing a programme that requires few 2-D character arrays from user input, then store those arrays in a text file? I think, to work this programme out, you should place some identifier or say a divider(e.g. ' | ') in that text file between each 2-D array....and so on...
    Last edited by choykawairicky; 05-13-2004 at 09:44 AM.

  7. #7
    Registered User abrege's Avatar
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    Thanks for the help guys, here's my finished code

    Code:
    #include <iostream>
    #include <fstream>
    using namespace std;
    
    #define MAP_WIDTH 70
    #define MAP_HEIGHT 22
    
    void readMap(char map[MAP_HEIGHT][MAP_WIDTH])
    {
    	ifstream fin;
    	fin.open("test.txt");
    
    	for(int i = 0; i < MAP_HEIGHT; i ++)
    	{
    		for(int t = 0; t < MAP_WIDTH; t ++)
    			fin >> map[i][t];
    	}
    
    	fin.close();
    }
    
    void dispMap(char map[MAP_HEIGHT][MAP_WIDTH])
    {
    	for(int i = 0; i < MAP_HEIGHT; i ++)
    	{
    		for(int t = 0; t < MAP_WIDTH; t ++)
    		{
    			if(map[i][t] == '0')
    				cout << ' ';
    			else if(map[i][t] == '1')
    				cout << '.';
    			else if(map[i][t] == '2')
    				cout << '#';
    		}
    
    		cout << endl;
    	}
    }
    
    int main()
    {
    	char map[MAP_HEIGHT][MAP_WIDTH];
    
    	readMap(map);
    	dispMap(map);
    
    	return 0;
    }
    Works nicely
    I am against the teaching of evolution in schools. I am also against widespread
    literacy and the refrigeration of food.

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