I am trying to read a text file into an array of integers but my read doesn't affect anything and my array stays at its default value of 0, my code is as follows
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
ofstream myfile;
int a[1000] = {0};
myfile.open ("Euler7.txt", ios::out | ios::app | ios::binary);
for (int i=0;i<1000;i++)
{
myfile << a[i];
cout << a[i] << endl;
}
myfile.close();
int c = 0;
for (int b=0;b>995;b++)
{
if (a[b]*a[b+1]*a[b+2]*a[b+3]*a[b+4] > c)
c = a[b]*a[b+1]*a[b+2]*a[b+3]*a[b+4];
}
cout << c << a[0];
return 0;
}
i suspect i need an fin.ignore somewhere in there somewhere, but my skills with files go about as far as #include , the file i am trying to open goe something like
6717653133062491922511967442657474235534919493496983520312774506326239578318
No spaces or separation between numbers. i need each item of the array to hold an individual digit, there are 1000 numbers in the file.
Your file stream object is an ofstream, which is for writing out to a file. Instead, you want ifstream, which is for input. You'll also want to get rid of the ios::out and ios::app flags in the call to open. In addition, you're using operator << which is for output, rather than >> for input.
Seems like the fstream technique wasn't needed at all to solve this problem. Special thanks to Tacet for parts of this code:
#include <iostream>
#include <string>
using namespace std;
int _tmain(int argc, _TCHAR* argv[])
{
int pause;
string series="7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450";
unsigned int max = 0; //if it can not be less than zero, use a unsigned type
const unsigned int end = series.size()-4;
for (int i=0;i<end;i++)
if ((series[i]-'0')*(series[i+1]-'0')*(series[i+2]-'0')*(series[i+3]-'0')*(series[i+4]-'0') > max)
max = (series[i]-'0')*(series[i+1]-'0')*(series[i+2]-'0')*(series[i+3]-'0')*(series[i+4]-'0');
cout << max << '\n';
cin >> pause;
return 0;
}
Related
Making a program that reads integers from a file and creates an array, I have that part completed however I am trying to figure out how to change the SIZE value depending on how many ints are in the file. This file has 15 integers but another file may have more and this array will not take in all the ints.
using namespace std;
const int SIZE = 15;
int intArray[SIZE];
void readData(istream& inFile) {
for (int i = 0; i < SIZE; i++){
inFile >> intArray[i];
cout << intArray[i] << " ";
}
}
int main() {
ifstream inFile;
string inFileName = "intValues.txt";
inFile.open(inFileName.c_str());
int value, count = 0;
while(inFile >> value){
count += 1;
}
cout << count;
readData(inFile);
return 0;
}
As you can see I have a while loop counting the number of ints in the file however when I assign that to the size value I was running into many different issues.
A fixed-sized array simply cannot be resized, period. If you need an array whose size can change at runtime, use std::vector instead.
More importantly, you are reading through the entire file just to count the number of integers, and then you are trying to read the values from where the previous loop left off. You are not seeking the ifstream back to the beginning of the file so you can re-read what you have already read.
Try something more like this instead:
#include <iostream>
#include <fstream>
#include <vector>
#include <string>
using namespace std;
int main() {
string inFileName = "intValues.txt";
ifstream inFile(inFileName.c_str());
int value, count = 0;
while (inFile >> value){
++count;
}
cout << count;
std::vector<int> intArray;
intArray.reserve(count);
inFile.seekg(0);
while (inFile >> value){
intArray.push_back(value);
cout << value << " ";
}
// use intArray as needed...
return 0;
}
Alternatively, don't even bother counting the integers, just let the std::vector grow as needed, eg:
#include <iostream>
#include <fstream>
#include <vector>
#include <string>
using namespace std;
int main() {
string inFileName = "intValues.txt";
ifstream inFile(inFileName.c_str());
vector<int> intArray;
int value;
while (inFile >> value){
intArray.push_back(value);
cout << value << " ";
}
// use intArray as needed...
// you an get the count from intArray.size()
return 0;
}
I'm studying C++ and I don't know how to read blank word(like " ")
my code just reading only "words"
please help me
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main(int argc, char const *argv[]) {
ofstream output("data4.dat", ios::out | ios::binary);
string buffer = "A program that translates a high level languageto a machine language\n is called a compiler. A compiler is thus a somewhat peculiar sort\n of program and its output is yet another program. To avoid confusion,\n the input program is usually called the source program or\n source code, and the translated version produced by the compiler is called";
output << buffer;
output.close();
ifstream is;
ifstream input("data4.dat", ios::in | ios::binary);
string in_buffer;
if (! is.eof()) {
for ( int i = 0; i < sizeof(input); i++) {
input >> buffer[i];
}
}
input.close();
std::cout << buffer[2] << '\n';
return 0;
}
I am having difficulty populating an array from a .txt file. I can do it without the while loop if I already know the size of the file. However, once I incorporate a while loop to extract the file size the input odes not configure correctly. Pleas take a look over my code an let me know if you see where I am going wrong.
#include "stdafx.h"
#include <iostream>
#include <cmath>
#include <string>
#include <fstream>
int main()
{
using namespace std;
const char *inName_1 = "Instance_1.txt";
const char *inName_2 = "Instance_2.txt";
int arraySize_1 = 0, arraySize_2 = 0;
int array_1[20];
int array_2[20];
int number;
ifstream A2_file_1(inName_1);
if (A2_file_1.fail())
{
cout << "File 1 not open!" << '\n';
}
while (!A2_file_1.eof())
{
arraySize_1++;
A2_file_1 >> number;
}
if (A2_file_1.is_open())
{
for (int i = 0; i < arraySize_1; i++)
{
A2_file_1 >> array_1[i];
}
A2_file_1.close();
}
cout << "The size of the array 1 is: " << arraySize_1 << endl;
for (int i = 0; i < arraySize_1; i++)
{
cout << array_1[i] << endl;
}
return 0;
}
To read an arbitrary amount of numeric values from a text-file, all you need is an std::vector and a couple of std::istreambuf_iterator objects.
Then is as simple as
std::ifstream input("Instance_1.txt");
std::vector<int> values(std::istreambuf_iterator<int>(input),
std::istreambuf_iterator<int>());
That's it. Those four lines of code (counting the empty line) will read all int values from the text file Instance_1.txt and place them into the vector values.
Hey guys I stuck working on an assignment in which I asked to write a program that lists the contents of a file.
#include<iostream>
#include<fstream>
using namespace std;
int main() {
string array[5];
ifstream infile("file_names.txt");
int x=0;
while(infile>>array[x++]){
for(int i=0;i<=x;i++){
infile >> array[i];
cout << array[i] << endl;}}
}
basically I have a file named "file_names.txt" that contains three strings and I want my program to list them.
you don't need two loops.
int main() {
int array_size=5;
string array[array_size];
ifstream infile("file_names.txt");
int x=0;int i=0;
while(i<array_size && infile>>array[i]){ //order is important here
cout << array[i] << endl;
i++;
}
}
Your assignment was
an assignment in which I asked to write a program that lists the contents of a file.
One way of printing the contents of a file could be
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main()
{
ifstream fin("my_file.txt", ios::in); // open input stream
if(!fin){ // check state, that file could be successfully opened
printf("Error opening file.");
return 1;
}
while(fin.peek() != EOF){
cout << (char)fin.get();
}
fin.close(); // close input stream
return 0;
}
This code demonstrates some basic C++ functionality like
opening an input stream, checking the state of the input stream and reading the contents character by character. Try to understand each step.
I know I can get to the same result like this
string array[50];
ifstream infile("file_names.txt");
for(int i=0; **i<3**; i++){
infile >> array[i];
cout << array[i] <<endl;}
But the whole point is to use a while loop because there might be more or less than 3 items
I am learning C++ in one of my classes and I am having difficulties storing the content of a .txt file into a c string.
I have figured out how to validate that the .txt file exists but when I try storing the characters into a c-string it crashes.
This is my most recent attempt:
char * fileContent[MAX_SIZE];
ifstream ifile(argv[1]);
while (int i = 0 < MAX_SIZE)
{
ifile >> fileContent[i];
cout << fileContent[i];
if (ifile.eof())
break;
i++;
}
ifile.close();
Every-time the console gets to the loop it crashes. Are there any suggestions to help make this work?
I need it to be a c-string so that I can run the c-string through other functions. I am still pretty new to C++.
The assignment states: "Reads a text file into memory, one byte at a time"
I hope what I am trying to do is this.
Thank you
You can use the following code to read from a text file and save the string as a C-string. The output file (output.txt) contains the c-string output.
#include <string>
#include <iostream>
#include <fstream>
int main()
{
freopen("input.txt","r",stdin);
freopen("output.txt","w",stdout);
char *out_c_string;
char ch;
int index=0;
while(cin >> ch)
out_c_string[index++] = ch;
for(int i=0; i<index; i++)
cout << out_c_string[i]; // the c string of the file :)
return 0;
}
There were few bugs in your code, try this:
#include <iostream>
#include <string>
#include <fstream>
using namespace std;
int MAX_SIZE = 128;
int main(int argc, char* argv[])
{
char fileContent[MAX_SIZE]; //bad idea never do that!
// use an std::vector<char> instead!
// and reverse a minimum amount of chars
// using `reserve` if you are after performance
ifstream ifile(argv[1]);
int i = 0;
while (i < MAX_SIZE)
{
ifile >> fileContent[i];
cout << fileContent[i];
if (ifile.eof())
break;
i++;
}
ifile.close();
}
Combining everyones answers, I got this as my function:
void get_file_info(char * argv, char (&fileContent) [MAX_SIZE], int & filesize ){
freopen(argv, "r", stdin);
char ch;
int index = 0;
while (cin >> noskipws >> ch)
fileContent[index++] = ch;
cout << endl << index << endl;
#if SHOW_DEBUG_CODE
for (int count = 0; count < index; count++)
cout << fileContent[count];
#endif
fclose(stdin);
}
It seems to work just fine. I will look into vectors my next free time but for right now, I am going to continue with char array.
Thank you for your suggestions.
I would do this. It's more general to cope with any size file.
void ReadFile(char*file,char**buff,int*size){
// Open file as binary putting file position at the end
ifstream is(file,ios::binary|ios::ate);
// Get the current file position, which is the file end
*size=is.tellg();
// Put file pointer back at the start
is.seekg(0,ios::beg);
// errors
if (!*size){
cout<<"Unable to open input file or file empty\n";
exit(9);
}
// allocate a buffer one bigger to allow for zero terminator
*buff=new char[*size+1];
// read the whole file in one hit
is.read(*buff,*size);
// Done. So close and zero delimit data.
is.close();
*(*buff+*size)=0;
}