Reading bidemensional char array from file C++

Question

So I need to read a grid from a file,the grid's width and lengths is always the same.The problem is when I try to cout it on the last line it only shows about a half of it.

#include <iostream>
#include <fstream>
#include <cstring>

using namespace std;
ifstream TestIn("test");


int main()
{

    char Grid[1000][1000],s[1000];

    int LungimeX,LungimeY,i,j;

    TestIn.getline(s,1000);
    //finding the length
    LungimeX=strlen(s);
    cout<<LungimeX<<endl;

    //finding the width
    while (!TestIn.eof()) {
        TestIn.getline(s,1000);
        LungimeY++;
    }
    cout<<LungimeY;

    //reset .eof
    TestIn.clear();
    TestIn.seekg(0, TestIn.beg);

    //get the grid into the array
    for(i=1;i<=LungimeY;i++) {
    for(j=1;j<=LungimeX;j++) {
        TestIn.get(Grid[i][j]);
    }}

    for(i=1;i<=LungimeY;i++){
    for(j=1;j<=LungimeX;j++){
        cout<<Grid[i][j];
    }}

    return 0;
}

So yeah,any ideas how to fix this?

http://stackoverflow.com/questions/5605125/why-is-iostreameof-inside-a-loop-condition-considered-wrong — πάντα ῥεῖ, Oct 14 '15 at 10:13
just a guess: does the input file contain end-of-line characters ('\n') ? Probably yes, so they get read into Grid, which you don't want. Another thing is that your use arrays as 1'based, the indices in C++ begin with 0. Grid[0][1000] is wrong. — marek.jancuska, Oct 14 '15 at 10:19

score 0 · Answer 1 · answered Oct 14 '15 at 10:22

0

LungimeY isn't initialized
Need to read (to skip) the header line after the file rewind
Need to skip CR and/or LF characters after each line read when filling the array

answered Oct 14 '15 at 10:22

AndreyS Scherbakov

2,674
2
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27

score 0 · Answer 2 · answered Oct 14 '15 at 10:28

You were not ignoring the newline character LungimeX is the length of the line not including the new line character. a simple solution could be when reading the file if newline character is encountered read the next character. #include #include #include

using namespace std;
ifstream TestIn("test");


int main()
{

    char Grid[1000][1000],s[1000];

    int LungimeX,LungimeY,i,j;

    TestIn.getline(s,1000);
    //finding the length
    LungimeX=strlen(s);
    cout<<LungimeX<<endl;

//finding the width
            while (!TestIn.eof()) {
                TestIn.getline(s,1000);
            LungimeY++;}
cout<<LungimeY;

//reset .eof
TestIn.clear();
TestIn.seekg (0, TestIn.beg);

//get the grid into the array
for(i=1;i<=LungimeY;i++){
for(j=1;j<=LungimeX;j++){
    TestIn.get(Grid[i][j]);
    if(Grid[i][j] == '\n') //check new line character
       TestIn.get(Grid[i][j]);
}}

for(i=1;i<=LungimeY;i++){
for(j=1;j<=LungimeX;j++){
    cout<<Grid[i][j];
}
cout<<endl;
}



    return 0;
}

And yes Please use 0 indexing in C++ you are wasting memory this way.

score 0 · Answer 3 · answered Oct 14 '15 at 10:39

What about this kind of more C++ approach ?

#include <iostream>
#include <fstream>
#include <string>

int main()
{
    std::string fname("test.txt");
    std::ifstream f(fname.c_str());

    std::vector<std::string> lines;
    std::string line;
    while(std::getline(f, line))
        lines.push_back(line);

    unsigned long int num_rows = lines.size();
    unsigned long int num_cols = 0;
    if(num_rows > 0)
        num_cols = lines[0].length();

    std::cout << "num_rows = " << num_rows << std::endl;
    std::cout << "num_cols = " << num_cols << std::endl;

    for(unsigned long int i = 0; i < num_rows; ++i)
    {
        for(unsigned long int j = 0; j < num_cols; ++j)
            std::cout << lines[i][j];
        std::cout << std::endl;
    }

    return 0;
}

Reading bidemensional char array from file C++

3 Answers3