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I am a young programmer who is trying to learn c++. i have a working csv.file. but i want to search for a specific number assigned to the name and then displays the name of what i'm looking for. i have the file here:
1,Bulbasaur,grass
2,Ivysaur, grass
3,Venusaur, grass
4,Charmander, fire
5,Charmeleon, fire
6,Charizard, fire
7,Squirtle, water
8,Wartortle, water
9,Blastoise, water
Code
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
ifstream ip("pokedex.csv");
string pokedexnum[9];
string pokemonName[9];
string pokemonType[9];
cout<<"please enter a pokemon number:"<<" ";
cin>>pokemonType[0];
while (ip.good()){
getline( ip, pokedexnum[0]);
getline( ip, pokemonName[0]);
getline( ip, pokemonType[0]);
}
cout<<"the pokemon that is:"<< " "<<pokedexnum[0]<< "is the pokemon called:"<< pokemonName[0];
ifstream close("pokedex.csv");
return 0;
}
when it runs
please enter a pokemon number: 1
the pokemon that is: is the pokemon called:8,Wartortle, water
could you please point out what i am doing wrong?
Among the issues in this code:
You're not using std::getline correctly for comma-separated data. The result is each pass is consuming three lines from your input file; not three values from each line.
You're also not using ip.good() correctly as a while-condition.
You're retaining your test value in the array, which will be overwritten on the first iteration pass, so it is lost.
You're ignoring potential IO failures with each std::getline invoke.
You're overwriting slot-0 in your arrays with each loop iteration.
Minor, ifstream close("pokedex.csv"); clearly isn't doing what you think it is. That just creates another fstream object called close on the given file name.
The later may be intentional for now, but clearly broken in the near future.
In reality, you don't need arrays for any of this. All you're doing is reading lines, and seem to want to test the input number against that of the CSV data first column, reporting the line that you find, then ending this.
So do that:
Read the input value to search for.
Open the file for scanning.
Enumerate the file one line at a time.
For each line from (3), use a string stream to break the line into the comma separated values.
Test the id value against the input from (1). If the same, report the result and break the loop; you're done.
The result is something like this:
#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
#include <cstdlib>
int main()
{
std::cout<<"please enter a pokemon number: ";
long num;
if (std::cin >> num && num > 0)
{
std::ifstream ip("pokedex.csv");
std::string line;
while (std::getline(ip, line))
{
std::istringstream iss(line);
std::string id, name, skill;
if (std::getline(iss, id, ',') &&
std::getline(iss, name, ',') &&
std::getline(iss, skill))
{
char *endp = nullptr;
long n = std::strtol(id.c_str(), &endp, 10);
if (id.c_str() != endp && n == num)
{
std::cout << "The pokemon that is: " << num << " is called: " << name << '\n';
break;
}
}
}
}
}
Admittedly untested, but it should work.
Whether you want to store the items in arrays at this point is entirely up to you, but it isn't needed to solve the somewhat abstract problem you seem to be attempting, namely finding the matching line and reporting the name from said-same. If you still want to store them in arrays, I suggest you craft a structure to do so, something like:
struct Pokemon
{
int id;
std::string name;
std::string skill;
};
and have a single array of those, rather than three arbitrary arrays that must be kept in sync.
Four issues jump out at me:
You store the user's input into pokemonType, but then also use pokemonType for reading data from your CSV file. The file input is going to overwrite the user input.
Your file input loop always references index 0. All of the lines from your data file are going into element 0. That's the main reason that even if the user inputs 1, the output is from the last line of the data file.
Your file reading loop is structured like you want to put one part of each data line into a different array, but what you've written actually reads three lines on every iteration, storing those lines into the three different arrays.
This isn't affecting your output, but the code ifstream close("pokedex.csv"); is written like you want to close the file stream you opened, but I do believe what this line actually does is create a new ifstream called close, and opens pokedex.csv attached to it. In other words, it's just like your other line ifstream ip("pokedex.csv"); but with close as the variable name instead of ip.
You are going to want to look into something called "string tokenization". Start with some web searches, apply what you read about to your code, and of course if you hit another snag, post a new question here to Stack Overflow, showing (as you did here) what you tried and in what way it isn't working.
Elaborating on #3, here's what how your data file is being read:
at the end of the 1st iteration of the file-reading loop, ...
pokedexnum[0] is "1,Bulbasaur,grass"
pokemonName[0] is "2,Ivysaur, grass"
pokemonType[0] is "3,Venusaur, grass"
at the end of the 2nd iteration of the file-reading loop, ...
pokedexnum[0] is "4,Charmander, fire"
pokemonName[0] is "5,Charmeleon, fire"
pokemonType[0] is "6,Charizard, fire"
at the end of the 3rd iteration of the file-reading loop, ...
pokedexnum[0] is "7,Squirtle, water"
pokemonName[0] is "8,Wartortle, water"
pokemonType[0] is "9,Blastoise, water"
And that's why
<< "is the pokemon called:"<< pokemonName[0];
outputs
is the pokemon called:8,Wartortle, water
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!)
AccountNumber Type Amount
15 checking 52.42
23 savings 51.51
11 checking 12.21
is my tab delmited file
i would like to be able to search for rows by the account number. say if i put in 23, i want to get that specific row. how would id do that?
also more advance, if i wanted to change a specific value, say amount 51.51 in account 23. how do i fetch that value and replace it with a new value?
so far im just reading in row by row
string line;
ifstream is("account.txt");
if (is.is_open())
{
while (std::getline(is, line)) // read one line at a time
{
string value;
string parseline;
std::istringstream iss(line);
getline(line, parseline);
cout << parseline << endl; // do something with the value
while (iss >> value) // read one value at at time from the line
{
//cout << line << " "; // do something with the value
}
}
is.close();
}
else
cout << "File cant be opened" << endl;
return 0;
Given that each line is of variable length there is no way to index to particular row without first parsing the entire file.
But I suspect your program will want to manipulate random rows and columns. So I'd start by parsing out the entire file. Put each row into its own data structure in an array, then index that row in the array.
You can use "strtok" to split the input up into rows, and then strtok again to split each row into fields.
If I were to do this, I would first write a few functions that parse the entire file and store the data in an appropriate data structure (such as an array or std::map). Then I would use the data structure for the required operations (such as searching or editing). Finally, I would write the data structure back to a file if there are any modifications.
i have a text file with data like the following:
name
weight
groupcode
name
weight
groupcode
name
weight
groupcode
now i want write the data of all persons into a output file till the maximum weight of 10000 kg is reached.
currently i have this:
void loadData(){
ifstream readFile( "inFile.txt" );
if( !readFile.is_open() )
{
cout << "Cannot open file" << endl;
}
else
{
cout << "Open file" << endl;
}
char row[30]; // max length of a value
while(readFile.getline (row, 50))
{
cout << row << endl;
// how can i store the data into a list and also calculating the total weight?
}
readFile.close();
}
i work with visual studio 2010 professional!
because i am a c++ beginner there could be is a better way! i am open for any idea's and suggestions
thanks in advance!
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <limits>
struct entry
{
entry()
: weight()
{ }
std::string name;
int weight; // kg
std::string group_code;
};
// content of data.txt
// (without leading space)
//
// John
// 80
// Wrestler
//
// Joe
// 75
// Cowboy
int main()
{
std::ifstream stream("data.txt");
if (stream)
{
std::vector<entry> entries;
const int limit_total_weight = 10000; // kg
int total_weight = 0; // kg
entry current;
while (std::getline(stream, current.name) &&
stream >> current.weight &&
stream.ignore(std::numeric_limits<std::streamsize>::max(), '\n') && // skip the rest of the line containing the weight
std::getline(stream, current.group_code))
{
entries.push_back(current);
total_weight += current.weight;
if (total_weight > limit_total_weight)
{
break;
}
// ignore empty line
stream.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
}
}
else
{
std::cerr << "could not open the file" << std::endl;
}
}
Edit: Since you wannt to write the entries to a file, just stream out the entries instead of storing them in the vector. And of course you could overload the operator >> and operator << for the entry type.
Well here's a clue. Do you see the mismatch between your code and your problem description? In your problem description you have the data in groups of four lines, name, weight, groupcode, and a blank line. But in your code you only read one line each time round your loop, you should read four lines each time round your loop. So something like this
char name[30];
char weight[30];
char groupcode[30];
char blank[30];
while (readFile.getline (name, 30) &&
readFile.getline (weight, 30) &&
readFile.getline (groupcode, 30) &&
readFile.getline (blank, 30))
{
// now do something with name, weight and groupcode
}
Not perfect by a long way, but hopefully will get you started on the right track. Remember the structure of your code should match the structure of your problem description.
Have two file pointers, try reading input file and keep writing to o/p file. Meanwhile have a counter and keep incrementing with weight. When weight >= 10k, break the loop. By then you will have required data in o/p file.
Use this link for list of I/O APIs:
http://msdn.microsoft.com/en-us/library/aa364232(v=VS.85).aspx
If you want to struggle through things to build a working program on your own, read this. If you'd rather learn by example and study a strong example of C++ input/output, I'd definitely suggest poring over Simon's code.
First things first: You created a row buffer with 30 characters when you wrote, "char row[30];"
In the next line, you should change the readFile.getline(row, 50) call to readFile.getline(row, 30). Otherwise, it will try to read in 50 characters, and if someone has a name longer than 30, the memory past the buffer will become corrupted. So, that's a no-no. ;)
If you want to learn C++, I would strongly suggest that you use the standard library for I/O rather than the Microsoft-specific libraries that rplusg suggested. You're on the right track with ifstream and getline. If you want to learn pure C++, Simon has the right idea in his comment about switching out the character array for an std::string.
Anyway, john gave good advice about structuring your program around the problem description. As he said, you will want to read four lines with every iteration of the loop. When you read the weight line, you will want to find a way to get numerical output from it (if you're sticking with the character array, try http://www.cplusplus.com/reference/clibrary/cstdlib/atoi/, or try http://www.cplusplus.com/reference/clibrary/cstdlib/atof/ for non-whole numbers). Then you can add that to a running weight total. Each iteration, output data to a file as required, and once your weight total >= 10000, that's when you know to break out of the loop.
However, you might not want to use getline inside of your while condition at all: Since you have to use getline four times each loop iteration, you would either have to use something similar to Simon's code or store your results in four separate buffers if you did it that way (otherwise, you won't have time to read the weight and print out the line before the next line is read in!).
Instead, you can also structure the loop to be while(total <= 10000) or something similar. In that case, you can use four sets of if(readFile.getline(row, 30)) inside of the loop, and you'll be able to read in the weight and print things out in between each set. The loop will end automatically after the iteration that pushes the total weight over 10000...but you should also break out of it if you reach the end of the file, or you'll be stuck in a loop for all eternity. :p
Good luck!
I had one of my friends send me this programming assignment so I could brush up on some of my C++ skills. Below is the program description and my proposed algorithm. Could someone please provide some feedback/alternative solutions:
Problem:
This program creates word search puzzles - Words are printed at random locations in a rectangular grid. Words may be horizontal or vertical and may be forward (left-to-right or top-to-bottom) or reversed (right-to-left or bottom-to-top). Unused grid squares are filled with random letters. The program should take a set of word lists as input and produce two files as output. The first lists, for each puzzle, the list of words in the puzzle, followed by the puzzle itself. The second should show where in each puzzle the words are located, without the random filler letters
Our input file contains the following:
A number n > 0 (representing the # of words in the puzzle) followed by that many words. For example:
3
FRODO
GIMLI
ARAGORN
N will not be larger than 10
We need to create the puzzle using a multidimensional array of size 12 x 12
Requirements:
1. Two output files - One containing the puzzle words and he puzzles, one with only the solutions and no filler characters
2.There needs to be as many horizontal words as there are vertical words
3. A 1/3 of the words needs to be reversed
4. There needs to be at least two intersections in the puzzle
Proposed Algorithm:
1. Create two multidimensional arrays - one for the puzzle and one for the solutions
2. Create a one-dimensional array that contains the various letters of the alphabet
3. Fill the puzzles array with random letters of the alphabet (using a pseudo-random # generator and the array from step # 2)
4. Begin reading the input file
5. Read in n
6. While counter is less than n, read in words, also have a counter for vertical words and horizontal words
7. For each word, find the length of the string
8. Find a random array location to insert the word.
9. If random location index + string length <= 12 or if random location index - string length is >= 0 (to ensure that the word will fit forward or reverse) insert the word
10. Also insert the word into the solutions array
12. Reuse arrays to insert all the words in the input file (in a similar manner)
I am still unsure as to how I can ensure that at least two intersections exist.
I am also concerned that my proposed algorithm is unnecessarily convoluted.
Your feedback is greatly appreciated!
OK, Here's as far as I got into the coding process, before I decided to go back and revisit the algorithm:
#include <iostream>
#include <fstream>
#include <iomanip>
#include <string>
#include <ctime>
using namespace std;
//Error Codes
const int INPUT_FAIL = 1;
const int PUZZLES_OUTPUT_FAIL = 2;
const int SOLUTIONS_OUTPUT_FAIL = 3;
//Function Declarations/Prototypes
void OpenFiles(ifstream& input, ofstream& puzzles, ofstream& solutions);
//PRE: The filestream objects exist and their address locations are passed in
//POST: The filestreams are opened. If they cannot be opened, an error message is printed to screen
// and the program is terminated.
void FillArray(char puzzle[][12], char alphabet[]);
//PRE: The address of the array is passed in
//POST: The array is filled with a random set of
void CreatePuzzle(char puzzle[][12], ifstream& input, ofstream& puzzles, ofstream& solutions);
//PRE: The address of the puzzle array,the address of the ifstream object and the addresses of the
// ofstream objects are passed in.
//POST: The data in the input file is read and the words are input into the puzzle AND the puzzle
// and solutions are printed to file.
void PrintPuzzle(char puzzle[][12], ofstream& output);
//PRE: The address of the puzzle array and the ofstream object is passed in
//POST: The puzzle is output to the file
int main()
{
//Seed the pseudo random generator
srand(time(NULL));
//Declare the filestream objects
ifstream input;
ofstream puzzles, solutions;
//Declare the 2D array
char puzzle[12][12];
char solution[12][12];
//Declare an alphabet array
char alphabet[27] = {"ABCDEFGHIJKLMNOPQRSTUVWXYZ"};
/*char alphabet[27] = {'A','B','C','D','E','F','G','H','I','J','K','L',
'M','N','O','P','Q','R','S','T','U','V','W',
'X','Y','Z'};*/
//Attempt to open files
OpenFiles(input, puzzles, solutions);
//Fill puzzle array with random letters of the alphabet
FillArray(puzzle, alphabet);
//Print puzzle
PrintPuzzle(puzzle, puzzles);
//Read in data to create puzzle
input >> numwords;
return 0;
}
//Function definitions
void OpenFiles(ifstream& input, ofstream& puzzles, ofstream& solutions)
{
//Attempt to open files
input.open("input.txt");
puzzles.open("puzzles2.txt");
solutions.open("solutions2.txt");
//Ensure they opened correctly
if (input.fail())
{
cout << "Input file failed to open!" << endl;
exit(INPUT_FAIL);
}
if (puzzles.fail())
{
cout << "Output file - puzzles.txt failed to open!" << endl;
exit(PUZZLES_OUTPUT_FAIL);
}
if (solutions.fail())
{
cout << "Output file - solutions.txt failed to open" << endl;
exit(SOLUTIONS_OUTPUT_FAIL);
}
}
void FillArray(char puzzle[][12], char alphabet[])
{
int tmp;
for(int i = 0; i < 12; i++)
{
for(int j = 0; j < 12; j++)
{
tmp = rand()%26;
puzzle[i][j] = alphabet[tmp];
}
}
}
void PrintPuzzle(char puzzle[][12], ofstream& output)
{
for(int i = 0; i < 12; i++)
{
for(int j = 0; j < 12; j++)
{
output << puzzle[i][j] << " ";
}
output << endl;
}
}
void CreatePuzzle(char puzzle[][12], ifstream& input, ofstream& puzzles, ofstream& solutions)
{
string pword; //#the puzzle word being read
int numwords; //# of words in a given puzzle
char tmparray[13];
int wordlength = 0;
int startloc;
//Read the number of words to be used in the puzzle
input >> numwords;
int vwords = numwords/2; //#of vertical words
int rwords = numwords/3; //# of reversed words
int hwords = (numwords - (numwords/2)); //# of horizontal words
for(int i = 0; i < numwords; i++)
{
//Read the word into our tmparray
input >> pword;
tmparray[] = pword;
wordlength = pword.length();
//Find a random array location to begin inserting the words
startloc = rand()%12;
int tmpcount = 0; //a temporary counter to ensure that
for(tmpcount; tmpcount <= 1; tmpcount ++)startloc + wordlength < 12)
{
for(int j = 0; j <= wordlength; j++)
{
puzzle[startloc][startloc]
Try it on paper first
Then make it work (in code)
Then make it fast /efficent / elegant
edit - Sorry I wasn't being sarcastic, this was before the OP posted code, and it wasn't clear they had attempted the problem.
My first suggestion would be don't bother pre-filling the array with anything - just stick th words in, and fill in the gaps randomly once you're finished.
A few thoughts/suggestions:
I think you could do this with one single 2D array instead of two. It seems simpler in my mind, though of course you may find I'm wrong when you sit down to actually implement this.
At step 9, instead of finding a spot where the word could fit either forward or reversed, first decide which way it's going to go in (perhaps using a random number generator). Then pick a spot and check the first condition, and just insert the word, either forwards or backwards. Remember this is a 2D array though, so you'll need to look at both the x and y coordinates of the point you chose. You'll also have to look at the words you've already placed in the grid, to make sure you don't overwrite something that's already there.
For finding intersections, think about how you would do it by hand (like Martin said). You've already placed a few words in the grid and now you want to add a new one. Suppose there aren't many intersections yet so you'd like to have the current word intersect one of the ones already in teh grid, if possible. How do you know if an intersection is possible, and how do you know where to place the word so that it creates an intersection?
My first thoughts are:
Place the words first and then randomly fill the gaps. I think it will be much easier for you to visualise it that way and also be easier to check if the word placement is done correctly.
After placing the first word I would save the word into an array. After checking if the second word is small enough to fit the puzzle I would have the program find the common letters of word 1 and 2. If they have a common letter, place the second word so the two words intersect(of course you must first check if the way you try to place word 2 is legal aka if it fits the puzzle the way you are trying to place it). Word 3 is the same way except look for possible intersections between words 1 and 2.If there is no possible intersection try the next word. If you can't have 2 or more intersections after placing all words, empty the array and replace the first word in a different random position. After having placed words in such a way that at least two intersections exist, you can continue and place the rest of the words.