I want to read just the first line of standard input, and place the the values into a vector (unknown number of entries). With each vector element holding a value (i.e. vector[1]=1, vector[2]=-30...)
E.g.
1 -30 10 300
I've tried just using a while loop and cin, but I can't seem to make it stop at the terminating character /n. And I've been trying to implement this with getline, but I'm having no luck. Is there a good method to store integers from standard input, into a vector?
Any help is appreciated,
Thank you in advance. :)
std::string line;
if( std::getline(std::cin, line) ) {
std::istringstream ss(line);
int i;
while(ss >> i) {
vec.push_back(i);
}
}
As an alternative you can also use istream iterators on ss.
The below code works fine for your problem. the answer from Mohit should use getline not readline
vector <int> vec;
string input;
getline(cin,input);
istringstream ss(input);
int num;
while (ss >> num)
{
vec.push_back(num);
}
vector<int>::iterator itr = vec.begin();
while (itr != vec.end())
{
cout << *itr << endl;
itr++;
}
The snippet prints back to the standard output.
Why you are not able to stop using cin is it ignores white-space and end of line \n.
Related
I am trying to read through a text file that can possibly look like below.
HI bye
goodbye
foo bar
boy girl
one two three
I am trying to take the lines with only two words and store them in a map, the first word would be the key and second word would be the value.
below is the code I came up with but I can't figure out how to ignore the lines that do not have two words on them.
this only works properly if every line has two words. I understand why this is only working if every line has two words but, I'm not sure what condition I can add to prevent this.
pair myPair;
map myMap;
while(getline(file2, line, '\0'))
{
stringstream ss(line);
string word;
while(!ss.eof())
{
ss >> word;
myPair.first = word;
ss >> word;
myPair.second = word;
myMap.insert(myPair);
}
}
map<string, string>::iterator it=myMap.begin();
for(it=myMap.begin(); it != myMap.end(); it++)
{
cout<<it->first<<" "<<it->second<<endl;
}
Read two words into a temporary pair. If you can't, do not add the pair to the map. If you can read two words, see if you can read a third word. If you can, you have too many words on the line. Do not add.
Example:
while(getline(file2, line, '\0'))
{
stringstream ss(line);
pair<string,string> myPair;
string junk;
if (ss >> myPair.first >> myPair.second && !(ss >> junk))
{ // successfully read into pair, but not into a third junk variable
myMap.insert(myPair);
}
}
let me suggest a little different implementation
std::string line;
while (std::getline(infile, line)) {
// Vector of string to save tokens
vector <string> tokens;
// stringstream class check1
stringstream check1(line);
string intermediate;
// Tokenizing w.r.t. space ' '
while(getline(check1, intermediate, ' ')) {
tokens.push_back(intermediate);
}
if (tokens.size() == 2) {
// your condition of 2 words in a line apply
// process 1. and 2. item of vector here
}
}
You can use fscanf for take input from file and sscanf for take input from string with format. sscanf return how many input successfully take with given format. so you can easily check, how many word have a line.
#include<stdio.h>
#include<stdlib.h>
#include <iostream>
using namespace std;
int main()
{
char line[100];
FILE *fp = fopen("inp.txt", "r");
while(fscanf(fp, " %[^\n]s", line) == 1)
{
cout<<line<<endl;
char s1[100], s2[100];
int take = sscanf(line, "%s %s", s1, s2);
cout<<take<<endl;
}
return 0;
}
I'm having a bit of a problem with extracting data from a simple .txt file with the getline command.
The txt file is very simple: a column of 400 numbers. I use a vector to store them with the following code:
int i = 0;
string line;
vector <double> vec;
while (getline(input, line))
{
vec.push_back(i);
N++;
input >> vec[i];
i++;
}
It correctly creates a vector of 400 elements but first line of txt file is ignored (I end up with vec[0] = 2nd line of txt file instead of 1st) and 399th element is 399 instead of the 400th line of txt file.
I tried several other ways to extract this data but it was unsuccessful.
Thank you for your help!
EDIT:
I have edited the code according to some of the remarks:
vector <double> vec;
string line;
double num;
while (getline(input, line))
{
input >> num;
vec.push_back(num);
}
Unfortunately, it still skips the first line of my text file.
EDIT 2 --> SOLUTION:
Thanks to all of your remarks, I realized that I was doing something wrong when using both getline and input >> num;
Here is how the problem was solved:
double num;
vector <double> vec;
while (input >> num)
{
vec.push_back(num);
}
You can read the entire file into a vector just by passing std::istream_iterator to std::vector constructor, without loops:
std::vector<int> v{
std::istream_iterator<int>{input},
std::istream_iterator<int>{}
};
E.g.:
#include <iostream>
#include <iterator>
#include <vector>
#include <exception>
template<class T>
std::vector<T> parse_words_into_vector(std::istream& s) {
std::vector<T> result{
std::istream_iterator<T>{s},
std::istream_iterator<T>{}
};
if(!s.eof())
throw std::runtime_error("Failed to parse the entire file.");
return result;
}
int main() {
auto v = parse_words_into_vector<int>(std::cin);
std::cout << v.size() << '\n';
}
You loose the first line due to reading from the file once more - here:
while (getline(input, line))
// ^^^^^^^ Here you read the first line
{
input >> num;
// ^^^^^^^^ Here you will read the second line
You told you want a vector of doubles - like:
std::vector<double> vec;
So you should use std::stod to convert the line read by getline into a double. Like:
while (std::getline(input, line))
{
// Convert the text line (i.e. string) to a floating point number (i.e. double)
double tmp;
try
{
tmp = stod(line);
}
catch(std::invalid_argument)
{
// Illegal input
break;
}
catch(std::out_of_range)
{
// Illegal input
break;
}
vec.push_back(tmp);
}
Don't do input >> num; inside the loop.
If you really want to use input >> num; then you shall not use getline. That is - you can use either but not both.
Change your while loop like below:-
while (getline(input, line))
{
vec.push_back(line);
//N++;
//input >> vec[i];
//i++;
}
Also try with below option
do{
vec.push_back(i);
//N++;
//i++;
}while (input >> vec[i++]);
You are starting by putting 0 in vector in first iteration:
vec.push_back(i);
then after you read first line you read next string, but stream get pointer from file is already in different place, so you override this 0 and skip first value from stream. What is worse that is oddly converted to double:
input >> vec[i];
This way you will get wrong.
Try this:
while (std::getline(file, line)) {
//In c++11
vec.emplace_back(std::stod(line));
//In c++ 98, #include <stdlib.h> needed
//vec.push_back(atof(line.c_str()));
}
This assumes you will always have proper file.
I have an input getline:
man,meal,moon;fat,food,feel;cat,coat,cook;love,leg,lunch
And I want to split this into an array when it sees a ;, it can store all values before the ; in an array.
For example:
array[0]=man,meal,moon
array[1]=fat,food,feel
And so on...
How can I do it? I tried many times but I failed!😒
Can anyone help?
Thanks in advance.
You can use std::stringstream and std::getline.
I also suggest that you use std::vector as it's resizeable.
In the example below, we get input line and store it into a std::string, then we create a std::stringstream to hold that data. And you can use std::getline with ; as delimiter to store the string data between the semicolon into the variable word as seen below, each "word" which is pushed back into a vector:
int main()
{
string line;
string word;
getline(cin, line);
stringstream ss(line);
vector<string> vec;
while (getline(ss, word, ';')) {
vec.emplace_back(word);
}
for (auto i : vec) // Use regular for loop if you can't use c++11/14
cout << i << '\n';
Alternatively, if you can't use std::vector:
string arr[256];
int count = 0;
while (getline(ss, word, ';') && count < 256) {
arr[count++] = word;
}
Live demo
Outputs:
man,meal,moon
fat,food,feel
cat,coat,cook
love,leg,lunch
I don't want to give you some code because you must be new at C++ and you have to learn by yourself but I can give an hint: use substring to store it into a vector of string.
Okay, so I'm having a bit of a problem here. The thing is this code works on a friend's computer but I'm getting segmentation faults when I try to run it.
I am reading a file looking like so:
word 2 wor ord
anotherword 7 ano oth the her erw wor ord
...
And I want to parse every word of the file. The first two words (e.g. word and 2) are to be erased but saving the first one in another variable in the process.
I've looked around a bit on accomplishing this, and I've come up with this half-assed piece of code that seems to work on my friends' computer but not mine.
Dictionary::Dictionary() {
ifstream ip;
ip.open("words.txt", ifstream::in);
string input;
string buf;
vector<string> tokens; // Holds words
while(getline(ip, input)){
if(input != " ") {
stringstream ss(input);
while(ss >> buf) {
tokens.push_back(buf);
}
string werd = tokens.at(0);
tokens.erase(tokens.begin()); // Remove the word from the vector
tokens.erase(tokens.begin()); // Remove the number indicating trigrams
Word curr(werd, tokens);
words[werd.length()].push_back(curr); // Put the word at the vector with word length i.
tokens.clear();
}
}
ip.close();
}
What's the best of of parsing this kind of structure in a file and removing the first two elements but saving the others? As you can see, I'm making a Word object that contains a string and a vector for later use.
Regards
EDIT; It seems to add the first line fine, but on removal of the second element, it crashes with a segmentation fault error.
EDIT; words.txt contain this:
addict 4 add ddi dic ict
sinister 6 ini ist nis sin ste ter
test 2 est tes
cplusplus 7 cpl lus lus plu plu spl usp
Without leading blank spaces or ending blanks. Not that it reads all the way anyway.
Word.cc:
#include <string>
#include <vector>
#include <algorithm>
#include "word.h"
using namespace std;
Word::Word(const string& w, const vector<string>& t) : word(w), trigrams(t) {}
string Word::get_word() const {
return word;
}
unsigned int Word::get_matches(const vector<string>& t) const {
vector<string> sharedTrigrams;
set_intersection(t.begin(),t.end(), trigrams.begin(), trigrams.end(), back_inserter(sharedTrigrams));
return sharedTrigrams.size();
}
First of all, there is error in the number of closing }s in your posted code. If you indent them properly, you will see that your code is:
while(getline(ip, input))
{
if(input != " ")
{
stringstream ss(input);
while(ss >> buf) {
tokens.push_back(buf);
}
}
string werd = tokens.at(0);
tokens.erase(tokens.begin());
tokens.erase(tokens.begin());
Word curr(werd, tokens);
words[werd.length()].push_back(curr);
tokens.clear();
}
}
Assuming that is a small typo in posting, the other problem is that tokens is an empty list when input == " " yet you continue to use tokens as though it has 2 or more items in it.
You can fix that by moving everything inside the if statement.
while(getline(ip, input))
{
if(input != " ")
{
stringstream ss(input);
while(ss >> buf) {
tokens.push_back(buf);
}
string werd = tokens.at(0);
tokens.erase(tokens.begin());
tokens.erase(tokens.begin());
Word curr(werd, tokens);
words[werd.length()].push_back(curr);
tokens.clear();
}
}
I would add further checks to make it more robust.
while(getline(ip, input))
{
if(input != " ")
{
stringstream ss(input);
while(ss >> buf) {
tokens.push_back(buf);
}
string werd;
if ( !tokens.empty() )
{
werd = tokens.at(0);
tokens.erase(tokens.begin());
}
if ( !tokens.empty() )
{
tokens.erase(tokens.begin());
}
Word curr(werd, tokens);
words[werd.length()].push_back(curr);
tokens.clear();
}
}
You forgot to include the initialization of the variable "words" in your code. Just looking at it, I am guessing you are initializing "words" to be a fixed-length array of vectors, but then read a word that is off the end of the array. Bang, you're dead. Add a check to "werd.length()" to ensure it is strictly less than the length of "words".
ifstream ip;
ip.open("words.txt", ifstream::in);
string input;
while(getline(ip, input)){
istringstream iss(input);
string str;
unsigned int count = 0;
if(iss >> str >> count) {
vector<string> tokens { istream_iterator<string>(iss), istream_iterator<string>() }; // Holds words
if(tokens.size() == count)
words[str.length()].emplace_back(str, tokens);
}
}
ip.close();
This is what I used to make it work.
Quick question: I am trying to accept a string parameter and then print it backwards using stacks and vectors. However, nothing is printed to the screen after it says Here you go!. I believe it has something to do with the vector setup, as I have never worked with this before. Here is the code in question. I would appreciate any help!
void main() {
stack<char> S;
string line;
vector<char> putThingsHere(line.begin(), line.end());
vector<char>::iterator it;
cout << "Insert a string that you want to see backwards!" << endl;
cin >> line;
for(it = putThingsHere.begin(); it != putThingsHere.end(); it++){
S.push(*it);
}
cout << "Here you go! " << endl;
while(!S.empty()) {
cout << S.top();
S.pop();
}
system("pause");
}
Your vector is being initialized too early, when line is still empty. Move the construction of putThingsHere below the instruction that extracts the string from the standard input:
cin >> line;
vector<char> putThingsHere(line.begin(), line.end());
Here is a live example of your fixed program running correctly.
Notice the use of getline() instead of cin >> line, so that whitespaces in between your characters could still be read as part of one single string.
This said, it is worth mentioning that std::string satisfies the requirements of standard sequence containers and, in particular, has member functions begin() and end() returning an std::string::iterator.
Therefore, you do not need an std::vector<> at all and the snippet below will do the job:
getline(cin, line);
for(std::string::iterator it = line.begin(); it != line.end(); it++) {
S.push(*it);
}
Your line variable is initially empty. You never really put anything inside the vector PutThingsHere and stack S.
Put the
cout << "Insert a string that you want to see backwards!" << endl;
cin >> line;
before the vector<char> PutThingsHere(...) statement.
First read into line and only then putThingsTHere
stack<char> S;
string line;
cout << "Insert a string that you want to see backwards!" << endl;
cin >> line;
vector<char> putThingsHere(line.begin(), line.end());
vector<char>::iterator it;
I've your using std::string already, why not use:
`std::string reversed(line.rend(), line.rbegin());`