How do I read int and char from a file into an array

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The file has values like this
BECDCBAADEBACBAEDDBEDCBAAECDCB
1234 BECDXACDXAXDXEDBXCABCDEXX

The first line are right answers and are to be compared to the answers in the second (only has one line because of testing reasons) and the integer is the id.

What I have tried:

#include <iostream>
#include <fstream>
using namespace std;
int main(){
    char right[30],r;
    char n=0,m=0;
    char answers[30],a;
    int id[30],i=0;


    ifstream infile;
    infile.open("exam.txt");

    ofstream outfile;
    outfile.open("report.txt");

    if (!infile.is_open())
        cout<<"Error opening file. Aborting....";

    if (!outfile.is_open())
        cout<<"Error opening file. Aborting....";



    infile>>r;
    while (!infile.eof()&& n<30 && i<30){
        right [n] = r;
        infile>>id[i];
        cout<<right [n];
        cout<<id[i];
        n++;
        m++;
    }

Posted 18-Mar-17 10:11am

Member 13068214

Updated 19-Mar-17 2:11am

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Comments

Richard Andrew x64 18-Mar-17 18:59pm

This is ALMOST a good question because it contains the problem and what has been tried. But it's missing the crucial ingredient of exactly what the question is. What is it supposed to do, and what is it doing wrong?

Member 13068214 18-Mar-17 21:09pm

Oh here is the full thing

A multiple-choice examination consists of thirty questions. Each question has five choices, labeled A, B, C, D, and E. The first line of data contains the correct answers to the thirty questions in the first 30 character positions, for example:

BECDCBAADEBACBAEDDBEDCBAAECDCB

Each subsequent line contains the answers for a candidate. Data on a line consists of a candidate number (an integer), followed by one or more spaces, followed by the thirty answers given by the candidate in the next thirty consecutive character positions. An X is used if a candidate did not answer a partiular question. You may assume that a candidate number is followed by 30 valid responses A sample line is as follows:

1234 BECDXACDXAXDXEDBXCABCDEXX

There are an unknown number of candidates. A line containing a candidate number of 0 only indicates the end of the data.

Member 13068214 18-Mar-17 21:11pm

The thing is I'm trying to read the correct answers to an array but I'm getting an error when i reach the next line with the integers and I'm also reading the blank spaces when I'm supposed to ignore it.

Richard MacCutchan 19-Mar-17 4:35am

It would be much easier just to read each line into the array in one go using getline().

Member 13068214 19-Mar-17 6:13am

I can't use getline(). I'm doing a beginners programming course

Richard MacCutchan 19-Mar-17 8:46am

Then you need to find some way to know when you have reached the end of each line, and skip to the next one. What you have coded above does not appear to do what you want. In general it is always best to try and read, and parse, your input data first, and store it in some containers in your code. Once you have captured the information you can process it in whatever way necessary, before writing out your results.

1 solution

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

RAMASWAMY EKAMBARAM · Answer 1 · 2017-03-19T02:11:00

The following program (in C not C++) reads single characters - I hope you will be able to convert to C++. It's rather long but the C++ version (with all the built in classes and methods) may be shorter.

#include <stdio.h>
#include <ctype.h>

#define CR				13
#define LF				10
#define NUMQUESTIONS	30

typedef struct
{
	char standard[NUMQUESTIONS];
	int candidatenum;
	char ans[NUMQUESTIONS * 2 + 1];
	char eval[NUMQUESTIONS * 7 + 15];
}
EXAM, *PEXAM;

int readstandard(PEXAM pex, FILE *fp);
int processpaper(PEXAM pex, FILE *fp);

char *infile = "exam.txt", *outfile = "report.txt";


void main()
{
	FILE *fpin, *fpout;
	static EXAM ex;
	
	fpin = fopen(infile, "rb");
	fpout = fopen(outfile, "w");
	
	if(fpin == NULL || fpout == NULL)
	{
		goto eofunction;
	}
	
	readstandard(&ex, fpin);
	while(processpaper(&ex, fpin))
	{
		fprintf(fpout, "Candidate: %d\nAnswers: %s\nEvaluation: %s\n\n", ex.candidatenum, ex.ans, ex.eval);
	}
	
	eofunction:
	if(fpin == NULL)
	{
		printf("Could not open input file: %s\n", infile);
	}
	else
	{
		fclose(fpin);
	}

	if(fpout == NULL)
	{
		printf("Could not open output file: %s\n", outfile);
	}
	else
	{
		fclose(fpout);
	}
	
}

int readstandard(PEXAM pex, FILE *fp)
{
	char c;
	int i = 0;
	
	do
	{
		fread(&c, 1, 1, fp);
		if(i < NUMQUESTIONS && isupper(c))
		{
			pex->standard[i++] = c;
		}
	}
	while(c != LF);  
	
	return i;
}

int processpaper(PEXAM pex, FILE *fp)
{
	char c = 0;
	int i = 0, written = 0, tot = 0, score;
	
	pex->candidatenum = 0;
	do
	{
		if(fread(&c, 1, 1, fp) > 0)
		{
			if(isdigit(c))
			{
				pex->candidatenum = pex->candidatenum * 10 + (c - '0');
			}
			
			if(i < NUMQUESTIONS && isupper(c))
			{
				sprintf(pex->ans + i * 2, "%c ", c);
				tot += score = c == 'X' ? 0 : (c == pex->standard[i] ? 2 : -1);
				written += sprintf(pex -> eval + written, "%d. %d ", i + 1, score);
				i++;
			}
		}
	}
	while(c != LF && c);  
	if(i)
	{
		sprintf(pex -> eval + written, "Total: %d", tot);
	}
	
	return i;
}

Sample input file:

Quote:
BECDCBAADEBACBAEDDBEDCBAAECDCB
1234 BEABCDXACDXAXDXEDBXCAXEBDXDEXX
117 ACBEXXXACDXAXDXEDBXCABCXBAEDDE
23456 BECDXACDXBEDCBAAEAXDXEDBXCABCX

How do I read int and char from a file into an array

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How do I read int and char from a file into an array

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