How do I accept an unknown number of lines in c++? Each line has two strings in it separated by a space. I tried the solutions mentioned in This cplusplus forum, but none of the solutions worked for me. One of the solutions works only when Enter is pressed at the end of each line. I am not sure if the \n char will be given at the end of my input lines. What are my options?
My current attempt requires me to press Ctrl+Z to end the lines.
#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>
using namespace std;
int main(){
string line;
while(cin>>line and cin.eof()==false){
cout<<line<<'\n';
}
return 0;
}
I would like to take an unknown number of strings as shown below:
cool toolbox
aaa bb
aabaa babbaab
Please don't flag this as a duplicate, I really tried all I could find! I tried the following solution on the above given link by m4ster r0shi (2201), but it did not work for me.
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
int main()
{
vector<string> words;
string word;
string line;
// get the whole line ...
getline(cin, line);
// ... then use it to create
// a istringstream object ...
istringstream buffer(line);
// ... and then use that istringstream
// object the way you would use cin
while (buffer >> word) words.push_back(word);
cout << "\nyour words are:\n\n";
for (unsigned i = 0; i < words.size(); ++i)
cout << words[i] << endl;
}
And this other solution also did not work: other soln, and I tried this SO post too: Answers to similar ques. This one worked for my example, but when I pass only one line of input, it freezes.
// doesn't work for single line input
#include <iostream>
#include <fstream>
#include <sstream>
#include <vector>
using namespace std;
int main(){
string line ="-1";
vector<string>data;
while(1){
cin>>line;
if(line.compare("-1")==0) break;
data.push_back(line);
line = "-1";
}
for(int i =0;i<data.size();i+=2){
cout<<data[i]<<' '<<data[i+1]<<'\n';
}
return 0;
}
If each line has two words separated by whitespace, then perhaps you should have a Line struct which contains two std::strings and overloads the >> operator for std::istream.
Then you can just copy from std::cin into the vector.
#include <iostream>
#include <vector>
#include <algorithm>
#include <iterator>
struct Line {
std::string first;
std::string second;
};
std::istream& operator>>(std::istream& i, Line& line) {
return i >> line.first >> line.second;
}
int main() {
std::vector<Line> lines;
std::copy(
std::istream_iterator<Line>(std::cin),
std::istream_iterator<Line>(),
std::back_inserter(lines)
);
for (auto &[f, s] : lines) {
std::cout << f << ", " << s << std::endl;
}
return 0;
}
A test run:
% ./a.out
jkdgh kfk
dfgk 56
jkdgh, kfk
dfgk, 56
I'm trying to convert a string of characters into their ASCII int values. However I cannot get this to work for one even one character in the string. I would expect a result of 72 when entering 'H', but it returns a 0 (the same for every character I've tried).
#include "stdafx.h"
#include <iostream>
#include <cstdlib>
#include <string>
using namespace std;
int main()
{
string a;
cin >> a;
const char * b = a.c_str();
int c = atoi(b);
cout << int(c) << endl;
}
Thanks in advance.
atoi parses the C-string interpreting its content as an integral number, i.e.
int i = atoi("123"); // i = 123
You don't want this: you want to know the ASCII value of every single character of the input string. To figure this out, you can use this code snippet:
#include <iostream>
#include <string>
using namespace std;
int main()
{
string a;
cin >> a;
for(int c: a)
cout << c << '\n';
}
I'm not quite used to the string library but simply type:
cout<<(int)a[pozition];
You can place that in a for like this.
for(int i=0;i<a.length();i++)
cout<<(int)a[i]<<endl;
You can just cast each character to an int
#include <iostream>
#include <string>
using namespace std;
int main()
{
string a;
cin >> a;
for (int i = 0; i < a.length(); i++) {
cout << (int) a[i] << endl;
}
}
I will have to take the input as a string.Then turn it to an integer.Then use it in calculations.
#include <iostream>
#include <bits/stdc++.h>
using namespace std;
int main()
{
string word;
cin>>word;
word=stol(word);
cout<<word;
return 0;
}
do not store it in word again because you declared word at first as string
so instead create another variable of type( int/float/double) and do the "stoi(word)"
(add this to your code and remove the word=stoi(word)" )
here is full code :
#include <iostream>
#include <string>
using namespace std;
int main()
{
int x;
string word;
cin>>word;
x=stoi(word);
//now you can use x in any mathematical operation you want
//try couting the x or (add, multiply,...etc to it)
}
My code is this But i am getting garbage values. how do i make it general so that anyone can use it?
#include <iostream>
#include <string>
using namespace std;
void main()
{
char ch[31];
cin.get(ch,31);
for (int i = 30; i >= 0; i--)
{
cout << ch[i];
}
system("pause");
}
You are taking garbage char from you empty cells.
You must first know the number of char inserted by the user
use reverse function from algorithm header file and use string instead of char.
#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
int main() {
string s;
getline(cin,s);
reverse(s.begin(),s.end());
cout<<s<<endl;
return 0;
}
I would like to read an input file in C++, for which the structure (or lack of) would be something like a series of lines with text = number, such as
input1 = 10
input2 = 4
set1 = 1.2
set2 = 1.e3
I want to get the number out of the line, and throw the rest away. Numbers can be either integers or doubles, but I know when they are one or other.
I also would like to read it such as
input1 = 10
input2=4
set1 =1.2
set2= 1.e3
so as to be more robust to the user. I think this means that it shouldn't be red in a formatted fashion.
Anyway, is there a smart way to do that?
I have already tried the following, but with minimal knowledge of what I've been doing, so the result was as expected... no success.
#include <stdio.h>
#include <stdlib.h>
#include <float.h>
#include <math.h>
#include <iostream>
#include <fstream>
#include <iomanip>
#include <cstdlib>
#include <boost/lexical_cast.hpp>
#include <string>
using namespace std;
using namespace boost;
int main(){
string tmp;
char temp[100];
int i,j,k;
ifstream InFile("input.dat");
//strtol
InFile.getline(temp,100);
k=strtol(temp,0,10);
cout << k << endl;
//lexical_cast
InFile.getline(temp,100);
j = lexical_cast<int>(temp);
cout << j << endl;
//Direct read
InFile >> tmp >> i;
cout << i << endl;
return 0;
}
Simply read one line at a time.
Then split each line on the '=' sign. Use the stream functionality do the rest.
#include <sstream>
#include <fstream>
#include <iostream>
#include <string>
int main()
{
std::ifstream data("input.dat");
std::string line;
while(std::getline(data,line))
{
std::stringstream str(line);
std::string text;
std::getline(str,text,'=');
double value;
str >> value;
}
}
With error checking:
#include <sstream>
#include <fstream>
#include <iostream>
#include <string>
int main()
{
std::ifstream data("input.dat");
std::string line;
while(std::getline(data,line))
{
std::stringstream str(line);
std::string text;
double value;
if ((std::getline(str,text,'=')) && (str >> value))
{
// Happy Days..
// Do processing.
continue; // To start next iteration of loop.
}
// If we get here. An error occurred.
// By doing nothing the line will be ignored.
// Maybe just log an error.
}
}
There are already some fine solutions here. However, just to throw it out there, some comments implied that Boost Spirit is an inappropriate solution for this problem. I'm not sure I completely disagree. However, the following solution is very terse, readable (if you know EBNF) and error-tolerant. I'd consider using it.
#include <fstream>
#include <string>
#include <boost/spirit.hpp>
using namespace std;
using namespace boost::spirit;
int main()
{
ifstream data("input.dat");
string line;
vector<double> numbers;
while(getline(data,line))
{
parse(line.c_str(),
*(+~ch_p('=') >> ch_p('=') >> real_p[push_back_a(numbers)]),
space_p);
}
}
Off the top of my head:
vector<double> vals(istream &in) {
vector<double> r;
string line;
while (getline(f, line)) {
const size_t eq = line.find('=');
if (eq != string::npos) {
istringstream ss(line.substr(eq + 1));
double d = 0;
ss >> d;
if (ss) r.push_back(d);
else throw "Line contains no value";
}
else {
throw "Line contains no =";
}
}
return r;
}
int main(int argc, char *argv[]) {
vector<double> vs = vals(ifstream(argv[1]));
}
C FTW (modified to handle doubles)
#include <stdio.h>
int
main ()
{
double num;
while (!feof (stdin))
if (1 == fscanf (stdin, "%*[^=] = %lf", &num))
printf ("%g\n", num);
return 0;
}
now that you are already using boost with lexical_cast, just parse each line with boost::split() and boost::is_any_of() into 1 2-element vector, with token_compress turned on.
the following code illustrates the parse, but skips the numeric conversion, which could be solved easily with boost lexical_cast.
#include <fstream>
#include <sstream>
#include <string>
#include <iostream>
#include <vector>
#include <boost/algorithm/string/split.hpp>
#include <boost/algorithm/string/classification.hpp>
#include <boost/foreach.hpp>
using std::string;
using std::cout;
using std::ifstream;
using std::stringstream;
using std::vector;
std::string file_to_string()
{
ifstream data("data.txt");
stringstream s;
s << data.rdbuf();
return s.str();
}
void print_parameter(vector<string>& v)
{
cout << v_para[0];
cout << "=";
cout << v_para[1];
cout << std::endl;
}
vector<string> string_to_lines(const string& s)
{
return v_lines;
}
int main()
{
vector<string> v_lines;
boost::split(v_lines, file_to_string(), boost::is_any_of("\n"), boost::token_compress_on);
vector<string> v_para;
BOOST_FOREACH(string& line, v_lines)
{
if(line.empty()) continue;
boost::split(v_para, line, boost::is_any_of(" ="), boost::token_compress_on);
// test it
print_parameter(v_para);
}
}
If you are devising this format, I would suggest adopting the INI file format.
The lightweight syntaxed INI format includes sections (allows you to have a little more structure in the format) which may or may not be desirable in your case:
I.e.
[section_1]
variable_1=value1
variable_2=999
[sectionA]
variable_A=value A
variable_B=111
The external links on this wikipedia page list a number of libraries that can be used for working with these types of files that extend/replace the basic GetPrivateProfileString functions from the Windows API and support other platforms.
Most of these would handle the space padded = sign (or at least before the = since a space after the = may be intentional/significant.
Some of these libraries might also have an option to omit [sections] if you don't want that (my own C++ class for handling INI like format files has this option).
The advantage to these libraries and/or using the Windows API GetPrivateProfileXXX functions is that your program can access specific variables
(I.e. get or set the value for variable_A from sectionA) without your program having to
write/scan/rewrite the entire file.
Here's my quickest STL solution:
#include <fstream>
#include <list>
#include <locale>
void foo()
{
std::fstream f("c:\\temp\\foo.txt", std::ios_base::in);
std::list<double> numbers;
while (!f.eof())
{
int c = f.get();
if (std::isdigit(c, std::locale::classic()) ||
c == '+' ||
c == '-' ||
c == '.')
{
f.putback(c);
double val;
f >> val;
if (f.fail()) {
f.clear(f.eof() ? std::ios_base::eofbit : std::ios_base::goodbit);
continue;
}
else
{
numbers.push_back(val);
}
}
}
}
Just tested this... it works, and doesn't require anything outside of the C++ standard library.
#include <iostream>
#include <map>
#include <string>
#include <algorithm>
#include <iterator>
#include <cctype>
#include <sstream>
using namespace std; // just because this is an example...
static void print(const pair<string, double> &p)
{
cout << p.first << " = " << p.second << "\n";
}
static double to_double(const string &s)
{
double value = 0;
istringstream is(s);
is >> value;
return value;
}
static string trim(const string &s)
{
size_t b = 0;
size_t e = s.size();
while (b < e && isspace(s[b])) ++b;
while (e > b && isspace(s[e-1])) --e;
return s.substr(b, e - b);
}
static void readINI(istream &is, map<string, double> &values)
{
string key;
string value;
while (getline(is, key, '='))
{
getline(is, value, '\n');
values.insert(make_pair(trim(key), to_double(value)));
}
}
int main()
{
map<string, double> values;
readINI(cin, values);
for_each(values.begin(), values.end(), print);
return 0;
}
EDIT: I just read the original question and noticed I'm not producing an exact answer. If you don't care about the key names, juts discard them. Also, why do you need to identify the difference between integer values and floating-point values? Is 1000 an integer or a float? What about 1e3 or 1000.0? It's easy enough to check if a given floating-point value is integral, but there is a clas of numbers that are both valid integers and valid floating-point values, and you need to get into your own parsing routines if you want to deal with that correctly.