C Code Read Integer Array From File

MadJuggla9

i fabricated a text file with some numbers in it *sperated by a return* i want to open the file and store the numbers in an array. so i tin can phone call up whatever number is in the position i want. im new to c++ so accept it easy, heres what i have so far

                                                              ifstream fsnumbers;     fsnumbers.open ("numbers.dat");      int assortment[35];             int counter = 0;     while (counter < 34)     {         fsnumbers >> assortment[counter];         cout << fsnumbers;         cout << endl;         counter++;     }

im lost on how to get stuff from a text file read and printed.

obs

Get ahead and endeavour this:

                              const int MAX_NUMBERS = 34; int array[MAX_NUMBERS];  ifstream fsnumbers; fsnumbers.open("numbers.dat");         for (int i = 0; i < MAX_NUMBERS; i++) {     // subtract 48 for ascii to int conversion     array[i] = fsnumbers.get() - 48; }

The reason yous subtract 48 is considering the .get() function returns the ascii integer code for whatever character is next in fsnumbers. As yous can run across from an ascii table, integers outset at number 48. The but problem with this method is yous really don't know how many characters y'all have inputted.

MadJuggla9

Go alee and try this:
                                  const int MAX_NUMBERS = 34; int array[MAX_NUMBERS];  ifstream fsnumbers; fsnumbers.open up("numbers.dat");         for (int i = 0; i < MAX_NUMBERS; i++) {     // subtract 48 for ascii to int conversion     array[i] = fsnumbers.get() - 48; }                                
The reason you subtract 48 is because the .get() part returns the ascii integer code for any character is next in fsnumbers. As you can see from an ascii table, integers commencement at number 48. The simply problem with this method is you really don't know how many characters y'all have inputted.

characters? ill have 35 lines composing of the numbers 1-35. sick increase information technology later perhaps

Shadow2531

Here'south another example using a vector instead, so you don't have to worry about arrays and sizes. Each chemical element in the vector is a string. (bold you lot just need to display the numbers. The loop at the end was not needed to print out each line. Information technology's there for example purposes.).

                              #include <iostream> #include <string> #include <vector> #include <cstdlib> #include <fstream>  using namespace std;  int main() {     const string file = "file.txt";     ifstream in(file.c_str());     if (!in) {         cout << endl << "Mistake reading " << file << endl;         go out(EXIT_FAILURE);     }     vector<string> nums;     for (string south; getline(in,southward); ) {         nums.push_back(south);     }     cout << endl;     for (size_t i = 0; i < nums.size(); i++) {         cout << nums.at(i) << endl;     } }

Here's the same affair just of int blazon so you can perform operations between elements and specify what file to read via a command line parameter.

                              #include <iostream> #include <string> #include <vector> #include <cstdlib> #include <fstream> #include <sstream>  using namespace std;  int toInt(const string& due south) {     stringstream catechumen;     convert << due south;     int i;     catechumen >> i;     render i; }  int primary(int argc, char *argv[]) {     if (argc == ii) {         const string file = argv[one];         ifstream in(file.c_str());         if (!in) {             cout << endl << "Mistake reading " << file << endl;             exit(EXIT_FAILURE);         }         vector<int> nums;         for (string south; getline(in,southward); ) {             nums.push_back( toInt(southward) );         }         cout << endl;         for (size_t i = 0; i < nums.size(); i++) {             cout << nums.at(i) << endl;         }         } else {         cout << endl << "Usage: file.exe filename" << endl;     } }

obs

characters? ill take 35 lines composing of the numbers i-35. ill increase information technology afterwards maybe

Oh, I encounter. This is quick and dirty but it should piece of work. There is a LOT this won't check for like making sure your input doesn't exceed the maximum size of an integer.

                              const int MAX_NUMBERS = 35; // # of lines const int MAX_NUM_SIZE = 12; // line size int assortment[MAX_NUMBERS]; char in[MAX_NUM_SIZE];  ifstream fsnumbers; fsnumbers.open("numbers.dat"); 	        for (int i = 0; i < MAX_NUMBERS; i++) {     fsnumbers >> in;     array[i] = atoi(in); }

Lord of Shadows

You lot accept washed everything alright, in the while loop you lot read a int from the file and stored it in array[counter]. But so yous endeavor to print out an fstream when your wanting to just print out the number y'all just read. Supervene upon "cout << fsnumbers;" with "cout << array[counter];"

                                                              ifstream fsnumbers;     fsnumbers.open ("numbers.dat");      int array[35];             int counter = 0;     while (counter < 34)     {         fsnumbers >> assortment[counter];         cout << fsnumbers;         cout << endl;         counter++;     }

Mulchman MM

That's nonetheless printing the fstream. This:

                              while (counter < 34)     {         fsnumbers >> array[counter];         cout << array[counter] << endl;         counter++;     }

would print the number you just read from the file.

----

You could fifty-fifty shorten information technology to:

                              while (counter < 34)     {         fsnumbers >> assortment[counter++];         cout << array[counter - 1] << endl;     }

and nevertheless non affect Large-Oh.

Lord of Shadows

That's however printing the fstream

Thats cause I just quoted his lawmaking for a quick reference of what I was talking nearly... lol

MadJuggla9

my friend told me i had a picky compiler and helped me end it with some assistance from you guys. works bang-up

cheers

C Code Read Integer Array From File

c++ storing a text file of numbers in an array

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