I'm doing a hangman project for school, and one of the requirements is it needs to read the pictures of the hanging man from a text file. I have set up a text file with the '-' char which means the end of one picture and start of the next one.
I have this for loop set up to read the file until the delimiting character and store it in an array, but when testing I am getting incomplete pictures, cut off in certain places.
This is the code:
string s;
ifstream scenarijos("scenariji.txt");
for(int i = 0; i < 10; i++ ) {
getline(scenarijos, s, '-');
scenariji[i] = s;
}
For the record, scenariji is an array with type of string
And here is an example of the text file:
example
From your example input, it looks like '-' can be part of the input image (look at the "arms" of the hanged man). Unless you use some other, unique character to delimit the images, you won't be able to separate them.
If you know the dimensions of the images, you could read them without searching for the delimiter by reading a certain amount of bytes from the input file. Alternatively, you could define some more complex rules for image termination, e.g. when the '-' character is the only character in the line. For example:
ifstream scenarijos("scenariji.txt");
string scenariji[10];
for (int i = 0; i < 10; ++i) {
string& scenarij = scenariji[i];
while (scenarijos.good()) {
string s;
getline(scenarijos, s); // read line
if (!scenarijos.good() || s == "-")
break;
scenarij += s;
scenarij.push_back('\n'); // the trailing newline was removed by getline
}
}
Related
In C++, I'd like to read from an input file which contains different kind of datas: first the name of a contestant (2 or more strings with whitespaces), then an ID (string without whitespaces, always beginning with a number), then another strings without ws and a numbers (the sports and their achieved places).
For example:
Josh Michael Allen 1063Szinyei running 3 swimming 1 jumping 1
I show you the code what I started to write and then stucked..
void ContestEnor::next()
{
string line;
getline(_f , line);
if( !(_end = _f.fail()) ){
istringstream is(line);
is >> _cur.contestant >> _cur.id; // here I don't know how to go on
_cur.counter = 0;
//...
}
}
Thank you for your help in advance.
You should look into using std::getline with a delimiter. This way, you can delimit on a space character and read until you find a string where the first character in a number. Here is a short code example (this seems rather homework-like, so I don't want to write too much of it for you ;):
std::string temp, id;
while (std::getline(_f, temp, ' ')) {
if (temp[0] >= 0 && temp[0] <= '9') {
id = temp;
}
// you would need to add more code for the rest of the data on that line
}
/* close the file, etc. */
This code should be pretty self-explanatory. The most important thing to know is that you can use std::getline to get data up until a delimiter. The delimiter is consumed, just like the default behavior of delimiting on a newline character. Thus, the name getline isn't entirely accurate - you can still get only part of a line if you need to.
What I'm trying to do in input file stream a text document, then evaluate each character by displaying information to the user and for the use of the rest of my code. The only question I have is, if I do a loop like
myIn >> ch;
while (myIn)
{
//proceeds with code
}
That reads from file input stream, how can I find the line number and position of that character I just read in?
For example on a text document like this
Hello
How are you
I want to read in H, and say that H was found in line one, position 0. Continuing, read in w, found in position 1 line 2. Without grabbing an entire string line of code?
The only way to get the line number and character position is to count them yourself:
char c;
unsigned int character_count = 0U;
unsigned int line_number = 0U;
while (in.get(c))
{
++character_count;
if (c == '\n')
{
++line_number;
// Optional:
// character_count = 0U;
}
}
Note: the expression in>>c will skip white spaces.
Add counters for the character and line, which yoyu increase manually in the while loop.
I'm really stuck with this problem I'm having for reading rows and columns from a text file. We're using text files that our prof gave us. I have the functionality running so when the user in puts "numrows (file)" the number of rows in that file prints out.
However, every time I enter the text files, it's giving me 19 for both. The first text file only has 4 rows and the other one has 7. I know my logic is wrong, but I have no idea how to fix it.
Here's what I have for the numrows function:
int numrows(string line) {
ifstream ifs;
int i;
int row = 0;
int array [10] = {0};
while (ifs.good()) {
while (getline(ifs, line)) {
istringstream stream(line);
row = 0;
while(stream >>i) {
array[row] = i;
row++;
}
}
}
}
and here's the numcols:
int numcols(string line) {
int col = 0;
int i;
int arrayA[10] = {0};
ifstream ifs;
while (ifs.good()) {
istringstream streamA(line);
col = 0;
while (streamA >>i){
arrayA[col] = i;
col++;
}
}
}
edit: #chris yes, I wasn't sure what value to return as well. Here's my main:
int main() {
string fname, line;
ifstream ifs;
cout << "---- Enter a file name : ";
while (getline(cin, fname)) { // Ctrl-Z/D to quit!
// tries to open the file whose name is in string fname
ifs.open(fname.c_str());
if(fname.substr(0,8)=="numrows ") {
line.clear();
for (int i = 8; i<fname.length(); i++) {
line = line+fname[i];
}
cout << numrows (line) << endl;
ifs.close();
}
}
return 0;
}
This problem can be more easily solved by opening the text file as an ifstream, and then using std::get to process your input.
You can try for comparison against '\n' as the end of line character, and implement a pair of counters, one for columns on a line, the other for lines.
If you have variable length columns, you might want to store the values of (numColumns in a line) in a std::vector<int>, using myVector.push_back(numColumns) or similar.
Both links are to the cplusplus.com/reference section, which can provide a large amount of information about C++ and the STL.
Edited-in overview of possible workflow
You want one program, which will take a filename, and an 'operation', in this case "numrows" or "numcols". As such, your first steps are to find out the filename, and operation.
Your current implementation of this (in your question, after editing) won't work. Using cin should however be fine. Place this earlier in your main(), before opening a file.
Use substr like you have, or alternatively, search for a space character. Assume that the input after this is your filename, and the input in the first section is your operation. Store these values.
After this, try to open your file. If the file opens successfully, continue. If it won't open, then complain to the user for a bad input, and go back to the beginning, and ask again.
Once you have your file successfully open, check which type of calculation you want to run. Counting a number of rows is fairly easy - you can go through the file one character at a time, and count the number that are equal to '\n', the line-end character. Some files might use carriage-returns, line-feeds, etc - these have different characters, but are both a) unlikely to be what you have and b) easily looked up!
A number of columns is more complicated, because your rows might not all have the same number of columns. If your input is 1 25 21 abs 3k, do you want the value to be 5? If so, you can count the number of space characters on the line and add one. If instead, you want a value of 14 (each character and each space), then just count the characters based on the number of times you call get() before reaching a '\n' character. The use of a vector as explained below to store these values might be of interest.
Having calculated these two values (or value and set of values), you can output based on the value of your 'operation' variable. For example,
if (storedOperationName == "numcols") {
cout<< "The number of values in each column is " << numColsVal << endl;
}
If you have a vector of column values, you could output all of them, using
for (int pos = 0; pos < numColsVal.size(); pos++) {
cout<< numColsVal[pos] << " ";
}
Following all of this, you can return a value from your main() of 0, or you can just end the program (C++ now considers no return value from main to a be a return of 0), or you can ask for another filename, and repeat until some other method is used to end the program.
Further details
std::get() with no arguments will return the next character of an ifstream, using the example code format
std::ifstream myFileStream;
myFileStream.open("myFileName.txt");
nextCharacter = myFileStream.get(); // You should, before this, implement a loop.
// A possible loop condition might include something like `while myFileStream.good()`
// See the linked page on std::get()
if (nextCharacter == '\n')
{ // You have a line break here }
You could use this type of structure, along with a pair of counters as described earlier, to count the number of characters on a line, and the number of lines before the EOF (end of file).
If you want to store the number of characters on a line, for each line, you could use
std::vector<int> charPerLine;
int numberOfCharactersOnThisLine = 0;
while (...)
{
numberOfCharactersOnThisLine = 0
// Other parts of the loop here, including a numberOfCharactersOnThisLine++; statement
if (endOfLineCondition)
{
charPerLine.push_back(numberOfCharactersOnThisLine); // This stores the value in the vector
}
}
You should #include <vector> and either specific std:: before, or use a using namespace std; statement near the top. People will advise against using namespaces like this, but it can be convenient (which is also a good reason to avoid it, sort of!)
I have a file which contains records of students in the following format.
Umar|Ejaz|12345|umar#umar.com
Majid|Hussain|12345|majid#majid.com
Ali|Akbar|12345|ali#geeks-inn.com
Mahtab|Maqsood|12345|mahtab#myself.com
Juanid|Asghar|12345|junaid#junaid.com
The data has been stored according to the following format:
firstName|lastName|contactNumber|email
The total number of lines(records) can not exceed the limit 100. In my program, I've defined the following string variables.
#define MAX_SIZE 100
// other code
string firstName[MAX_SIZE];
string lastName[MAX_SIZE];
string contactNumber[MAX_SIZE];
string email[MAX_SIZE];
Now, I want to pull data from the file, and using the delimiter '|', I want to put data in the corresponding strings. I'm using the following strategy to put back data into string variables.
ifstream readFromFile;
readFromFile.open("output.txt");
// other code
int x = 0;
string temp;
while(getline(readFromFile, temp)) {
int charPosition = 0;
while(temp[charPosition] != '|') {
firstName[x] += temp[charPosition];
charPosition++;
}
while(temp[charPosition] != '|') {
lastName[x] += temp[charPosition];
charPosition++;
}
while(temp[charPosition] != '|') {
contactNumber[x] += temp[charPosition];
charPosition++;
}
while(temp[charPosition] != endl) {
email[x] += temp[charPosition];
charPosition++;
}
x++;
}
Is it necessary to attach null character '\0' at the end of each string? And if I do not attach, will it create problems when I will be actually implementing those string variables in my program. I'm a new to C++, and I've come up with this solution. If anybody has better technique, he is surely welcome.
Edit: Also I can't compare a char(acter) with endl, how can I?
Edit: The code that I've written isn't working. It gives me following error.
Segmentation fault (core dumped)
Note: I can only use .txt file. A .csv file can't be used.
There are many techniques to do this. I suggest searching StackOveflow for "[C++] read file" to see some more methods.
Find and Substring
You could use the std::string::find method to find the delimiter and then use std::string::substr to return a substring between the position and the delimiter.
std::string::size_type position = 0;
positition = temp.find('|');
if (position != std::string::npos)
{
firstName[x] = temp.substr(0, position);
}
If you don't terminate a a C-style string with a null character there is no way to determine where the string ends. Thus, you'll need to terminate the strings.
I would personally read the data into std::string objects:
std::string first, last, etc;
while (std::getline(readFromFile, first, '|')
&& std::getline(readFromFile, last, '|')
&& std::getline(readFromFile, etc)) {
// do something with the input
}
std::endl is a manipulator implemented as a function template. You can't compare a char with that. There is also hardly ever a reason to use std::endl because it flushes the stream after adding a newline which makes writing really slow. You probably meant to compare to a newline character, i.e., to '\n'. However, since you read the string with std::getline() the line break character will already be removed! You need to make sure you don't access more than temp.size() characters otherwise.
Your record also contains arrays of strings rather than arrays of characters and you assign individual chars to them. You either wanted to yse char something[SIZE] or you'd store strings!
I've been working on a class assignment for C++ and we're required to acquire input from a text file and assign those values to an array....one is a string, the second an int, and the third a double.
We've only been introduced to arrays and I don't know anything yet about pointers or linked lists, or any of the higher end stuff, so I feel like I'm somewhat limited in my options. I've worked all day trying to figure out a way to acquire input from the text file and assign it to the appropriate array. I've tried to use getline to read the input file and set a delimiter to separate each piece of data but I get an error when I try to use it more than once. From what I've read, this has to do with how I'm overloading the function but I'm at a loss at resolving it. Every explanation I've read about it goes beyond my current level of familiarity. Right now, I'm focused on this fragment of code:
for (int i = 0; i < EMP_NUM; i++) // Get input from text file for names.
getline(inFile, nameAr[i], '*');
for (int i = 0; i < EMP_NUM; i++) // Input for hours.
getline(inFile, hoursAr[i], '*');
for (int i=0; i < EMP_NUM; i++) // Input for hourly rate.
getline(inFile, hrateAr[i], '*');
I'm trying to use getline three times and write the data to three separate arrays, then make a series of calculations with them later and output them to another text file. The first instance of getline doesn't produce any compiler errors but the latter two do. I'm not quite sure of another solution to get the data into my arrays, so I'm at a loss. Any help would be great!
If I understand correctly you merely have three values in a file: a string, an int and a double. I assume they are delimited by whitespace.
If that is so then you don't need std::getline(). Rather, use the extraction operator:
std::ifstream file("input.txt");
std::string s;
if( ! (file >> s) ) { // a single word extracted from the file
// failure
}
int n;
// ...
1) Instead of three different iteration, use only one
2) Pass string object in getline instead of pointers
string buf;
for (int i = 0; i < EMP_NUM; i++) // Get input from text file for names.
{
getline(inFile, buf, '*');
nameAr[i] = buf;
getline(inFile, buf, '*'); //assuming delimiter is again *
hoursAr[i] = atoi(buf.c_str() ); //C way to doing it...however in c++ u have to use stringstreams....
getline(inFile, buf);
hrateAr[i] = atof(buf.c_str() );;
}
What do the compiler errors say? Are you sure that the error is caused by getline? Maybe it's not because the getline calls but because of multiple declarations of i.