I'm having difficulties finding the problem here , the program must read a number N and then read 2 vectors with N lenght, multiply each number of the first vector with the relevant number of the second one and substract each of the previous multiplies (example A[0]*B[0] - A[1]*B[1] .... A[N-1]*B[N-1] ) Any replies will be greatly appreciated.
Input values : 3/
1 2 -3
/4 -5 -6
Output : -4
Here's the code:
#include <iostream>
#include <string>
#include <sstream>
#include <vector>
#include <cstdlib>
using namespace std;
/* Splits string using whitespace as delimeter */
void split_input(vector<double> &vector_values, const string &input)
{
char delim = ' ';
stringstream mySstream(input);
string temp;
while(getline(mySstream, temp, delim))
{
vector_values.push_back(atof(temp.c_str()));
}
}
double multiply(vector<double> &first_vector, vector<double> &second_vector)
{
double result = 0;
for(int i = 0; i < first_vector.size(); i++)
{
if (i == 0)
{
result = first_vector[i]*second_vector[i];
}
else
{
result -= first_vector[i]*second_vector[i];
}
cout << result << endl;
}
return result;
}
int main()
{
vector<double> first_vector;
vector<double> second_vector;
int num;
string input_values;
cout << "Please enter a number: " << endl;
cin >> num ;
/* Ignores the endline char from the previous cin */
cin.ignore();
/* Read first string, split it and store the values in a vector */
getline(cin, input_values);
split_input(first_vector, input_values);
cin.ignore();
/* Read second string, split it and store the values in a vector */
getline(cin, input_values);
split_input(second_vector, input_values);
/* Multiply vectors */
cout << multiply(first_vector, second_vector) << endl;
return 0;
}
Remove cin.ignore() after split_input(first_vector, input_values);. With cin.ignore() the first element of the second vector is alway 0. Your main() should look like this:
int main()
{
vector<double> first_vector;
vector<double> second_vector;
int num;
string input_values;
cout << "Please enter a number: " << endl;
cin >> num ;
/* Ignores the endline char from the previous cin */
cin.ignore();
/* Read first string, split it and store the values in a vector */
getline(cin, input_values);
split_input(first_vector, input_values);
// following line causes the first element of the second vector to become 0
// cin.ignore();
/* Read second string, split it and store the values in a vector */
getline(cin, input_values);
split_input(second_vector, input_values);
/* Multiply vectors */
cout << multiply(first_vector, second_vector) << endl;
return 0;
}
Related
I need to read a variable number of integers from keyboard so that I can use each of them.
First I thought I could use something like
int myinteger;
for (int i=0; i<MAX_NUMBER_OF_INTEGERS; i++){
cin >> myinteger;
//What I want to do with that Integer
}
But then I realized that if MAX_NUMBERS_OF_INTEGERS = 10 I have to write 10 integers. But what I want is that I can pass "1 2 3" "1 2 3 4" (for example) and not necessary write 10 integers.
The question seems to have changed a little bit since it was asked and a good answer was given. This just serves to answer the new questions.
#include <iostream>
#include <sstream>
#include <vector>
const int MAX_NUMBERS_OF_INTEGERS = 10;
int main() {
std::string line;
std::cout << "Enter at most " << MAX_NUMBERS_OF_INTEGERS << " ints, separated by spaces: ";
std::getline(std::cin, line);
// create a string stream of the line you entered
std::stringstream ss(line);
// create a container for storing the ints
std::vector<int> myInts;
// a temporary to extract ints from the string stream
int myInteger;
// extract at most MAX_NUMBERS_OF_INTEGERS ints from the string stream
// and store them in the container
while(myInts.size()<MAX_NUMBERS_OF_INTEGERS && ss>>myInteger) myInts.push_back(myInteger);
std::cout << "Extracted " << myInts.size() << " integer(s)\n";
// loop through the container and print all extracted ints.
for(int i : myInts) {
std::cout << i << "\n";
}
// ... or access a certain int by index
if(myInts.size() > 2)
std::cout << "The third int was: " << myInts[2] << "\n";
}
std::vector<int> read_ints;
int _temp;
for(;;)
{
cin >>_temp;
if(!cin.good()) {
break;
}
else {
read_ints.push_back(_temp);
}
}
I haven't tested this solution but it should read an arbitrary number of ints from cin until you enter something else than an integer. You could also skip the saving in the vector part if you don't need to save the results. This is just releveant if you want to save an arbitray number of integers.
EDIT: After clarification your solution could look like this:
int MAX_CHARS = 10;
int my_int;
cin >> setw(MAX_CHARS) >> my_int;
setw limits the number of input characters but you have to include iomanip header
If you want to access every digit, convert int to vector of ints with this function:
vector <int> integerToArray(int x)
{
vector <int> resultArray;
while (true)
{
resultArray.insert(resultArray.begin(), x%10);
x /= 10;
if(x == 0)
return resultArray;
}
}
then you can access each digit with the index e.g. first digit
vectory<int> resultArray = integerToArray(my_int);
int digit = resultArray[0];
Source
One way to read all numbers from a single line limiting them to a maximum number of integers is using std::getline() to get the line into a string then use istringstream in a loop.
#include <iostream>
#include <sstream>
using namespace std;
int main() {
std::string line;
std::getline (std::cin,line);
std::istringstream iss(line);
int myInt;
for(int i=0;(iss >> myInt) && (i < MAX_NUMBER_OF_INTEGERS);++i ) {
std::cout << myInt << ' ';
}
return 0;
}
Note: I did not define MAX_NUMBER_OF_INTEGERS in the code. I could have defined it with const int MAX_NUMBERS_OF_INTEGERS = 10; before usage or possibly that could be a preprocessor define or even a command line parameter. I leave this up to the user.
#include <iostream>
#include <string>
using namespace std;
int main() {
int n;cin>>n;//entering number of string to be inputed
string a[n];//declaring an array of type string
for(int i=0;i<n;i++){
cin>>a[i];
}
for(int i=0;i<n;i++){
cout<<a[i]<<endl;
}
//for manipulating letters of strings
cout<<a[0][1];
return 0;
}
To access the elements of a string, we should output the result as a multidimensional array. This seems a bit counter intuitive. Could someone explain is this the right way.
Input
2
asfdsf
asfdsafd
Output
asfdsf
asfdsafd
s
A string is an array of characters. So an array of strings is an array of arrays of characters. To access the jth character in the ith string, you use a[i][j].
You cannot declare:
string a[n]; //declaring an array of type string
Why?
ISO C++ forbids variable length array ‘a’
Instead, you should use a vector of string and .push_back() each new string you add, e.g.
#include <iostream>
#include <string>
#include <vector>
int main (void) {
int n = 0;
std::cout << "enter the number of strings: ";
std::cin >> n;
if (n < 1) {
std::cerr << "error: invalid number of strings.\n";
return 1;
}
std::vector <std::string> a; // vector of strings
for (int i = 0; i < n; i++) { /* read each string */
std::string tmp;
std::cin >> tmp; /* into a temp string */
if (!std::cin.eof() && !std::cin.fail()) /* validate read */
a.push_back(tmp); /* add string to vector */
/* output string and first character using indexes */
std::cout << "string[" << i << "]: " << a[i] << " (a[" << i
<< "][0]: " << a[i][0] << ")\n";
}
}
Example Use/Output
$ ./bin/stringindex
enter the number of strings: 4
My
string[0]: My (a[0][0]: M)
Dog
string[1]: Dog (a[1][0]: D)
Has
string[2]: Has (a[2][0]: H)
Fleas!
string[3]: Fleas! (a[3][0]: F)
Look things over and let me know if you have any questions.
I am new to c++ , Basically I belong to PHP . So I am trying to write a program just for practice, to sort an array . I have successfully created the program with static array value that is
// sort algorithm example
#include <iostream> // std::cout
#include <algorithm> // std::sort
#include <vector> // std::vector
bool myfunction (int i,int j) { return (i<j); }
struct myclass { bool operator() (int i,int j) { return (i<j);} } myobject;
int main () {
int myints[] = {55,82,12,450,69,80,93,33};
std::vector<int> myvector (myints, myints+8);
// using default comparison (operator <):
std::sort (myvector.begin(), myvector.begin()+4);
// using function as comp
std::sort (myvector.begin()+4, myvector.end(), myfunction);
// using object as comp
std::sort (myvector.begin(), myvector.end(), myobject);
// print out content:
std::cout << "myvector contains:";
for (std::vector<int>::iterator it=myvector.begin(); it!=myvector.end(); ++it)
std::cout << ' ' << *it;
std::cout << '\n';
return 0;
}
its output is ok . But I want that the elements should input from user with space separated or , separated . So i have tried this
int main () {
char values;
std::cout << "Enter , seperated values :";
std::cin >> values;
int myints[] = {values};
/* other function same */
}
it is not throwing an error while compiling. But op is not as required . It is
Enter , seperated values :20,56,67,45
myvector contains: 0 0 0 0 50
3276800 4196784 4196784
------------------ (program exited with code: 0) Press return to continue
You can use this simple example:
#include <iostream>
#include <string>
#include <sstream>
#include <algorithm>
using namespace std;
int main()
{
stringstream ss;
string str;
getline(cin, str);
replace( str.begin(), str.end(), ',', ' ');
ss << str;
int x = 0;
while (ss >> x)
{
cout << x << endl;
}
}
Live demo
or, if you want to have it more generic and nicely enclosed within a function returning std::vector:
#include <iostream>
#include <string>
#include <sstream>
#include <algorithm>
#include <vector>
using namespace std;
template <typename T>
vector<T> getSeparatedValuesFromUser(char separator = ',')
{
stringstream ss;
string str;
getline(cin, str);
replace(str.begin(), str.end(), separator, ' ');
ss << str;
T value{0};
vector<T> values;
while (ss >> value)
{
values.push_back(value);
}
return values;
}
int main()
{
cout << "Enter , seperated values: ";
auto values = getSeparatedValuesFromUser<int>();
//display values
cout << "Read values: " << endl;
for (auto v : values)
{
cout << v << endl;
}
}
Live demo
Read in all the values into one string, then use a tokenizer to separate out the individual values.
How do I tokenize a string in C++?
The above answers are very good for an arbitrary number of inputs, but if you allready know how many numbers will be put, you could do it like:
int[5] intList;
std::cin >> intList[0] >> intList[1] >> intList[2] >> intList[3] >> intList[4]
But please note that this method does not do any check if the numbers are put properly, so if there are for example letters or special characters in the input, you might get unexpected behavior.
Let's see what you wrote:
int main () {
char values;
std::cout << "Enter , seperated values :";
std::cin >> values; // read a single character
int myints[] = {values}; // create a static array of size 1 containing the single character converted to an int
/* other function same */
}
what you need is:
#include <sstream>
#include <string>
...
int main () {
std::cout << "Enter space seperated values :";
std::vector<int> myvector;
std::string line;
std::getline(std::cin, line); // read characters until end of line into the string
std::istringstream iss(line); // creates an input string stream to parse the line
while(iss >> value) // so long as values can be parsed
myvector.push_back(value); // append the parsed value to the vector
/* other function same */
}
If you want comma separated input you'll need to parse the comma as a single character in addition to the integer values.
What you are doing
int main () {
char values; //Declare space for one character
std::cout << "Enter , seperated values :"; //Ask user to enter a value
std::cin >> values; //Read into values (one value only)
int myints[] = {values}; // assign the first element to the ASCII code of whatever user typed.
/* other function same */
}
In the language char works as an 8-bit integer. Through function overloading, different behavior can be implemented. Read about static polymorphism for more details how it works.
What you need to do
std::vector<int> values;
char ch_in;
std::string temp;
while(cin.get(ch_in)) {
switch(ch_in) {
case ',':
case ' ': //Fall through
values.push_back(atoi(temp.c_str()); //include cstdlib for atoi
temp.clear();
break;
default:
temp+=ch_in;
}
}
You should put this in a separate function. With this skeleton, you can implement a more fancy syntax by adding more cases, but then you need something else than a std::vector<int> to put things into. You can (should?) also add error checking in the default case:
default:
if( (ch_in>='0' && ch_in<='9')
|| (temp.size()==0 && ch_in=='-') ) {
temp+=ch_in;
}
else {
cerr<<ch_in<<" is an illegal character here."
temp.clear();
}
#include <iostream>
#include <string>
#include <sstream>
#include <string.h>
using namespace std;
// THIS CODE IS TO GIVE ARRAY IN ONE LINE AND OF DESIRED LENGHT ALSO WITH NEGATIVE NUMBERS
// You can also do it by using ASCII but we Are using library name
// <sstream> to convert string charters to numbers
//O(n) time complexity
int main()
{
/*
// INPUT
// 7 array length
// 34-56-789 // without space b/w them */
int N;
cout << "Enter the size of the array " << endl;
cin >> N;
cout << "INPUT Without giving space b/w " << endl;
string strx;
cin >> strx;
int X[N]; // array to store num
int p = 0;
// NOTE USE HERE STRX.LENGHT() becouse we have to go through the whole string
for (int i = 0; i < strx.length(); i++)
{ // we have declare tempx to store a particular character
// one time
string tempx;
tempx = strx[i];
stringstream strtointx(tempx);
// this is the syntax to convert char to int using <sstream>
if (strx[i] == '-')
{
/*
The tricky point is when you give string as 1-23
here - and 2 are the separte characters so we are not
getting -2 as number but - and 2 so what we do is
we chek for '-' sign as the character next to it
will be treated as negative number
*/
tempx = strx[i + 1];
// by assigning strx[i+1] to tempx so that we can getting the which should be treated as negative number
stringstream strtointx(tempx);
// still it is a charter type now again using library
// convert it to int type
strtointx >> X[p];
X[p] = -X[p];
// now make that number to negative ones as we want it to be negative
i++;
// inside this if i++ will help you to skip the next charcter of string
// so you can get desired output
}
// now for all the positive ones to int type
else{ strtointx >> X[p]; }
p++; // finally increment p by 1 outside if and else block
}
// loop ends now get your desired output
cout<<"OUTPUT "<<endl;
for (int i = 0; i < N; i++)
{
cout << X[i] << " ";
}
cout<<endl;
cout<<"CODE BY MUKUL RANA NIT SGR Bch(2020)";
return 0;
}
// OUTPUT
/*
Enter the size of the array
7
INPUT Without giving space b/w
34-56-789
OUTPUT
3 4 -5 6 -7 8 9
CODE BY MUKUL RANA NIT SGR Bch(2020)
PS C:\Users\user\Desktop\study c++>
*/
// CAUTION :
/*
1) do not give input with spaces
**** if you do then first you have to change /chek the code for spaces indexes also ***
2)do not give charates as 56-89##13 as you want here only numbers
3) this only for integer if you want to float or double you have to do some changes here
because charters index and length would be difeerent in string.
*/
As Mehdi Algholipour wrote i wanted to
1.Get string from input
2.Separate input to Integer numbers
3.Save them into Array
cout << "Give me some integers separated with space";
cin >> string; // example input 10 210 300 510
//..some code that seperate input to integer numbers and save them to Array
//EXPECTED RESULT: Array[0]=10 Array[1]=210 etc...
I think your mean is:
Get string from input
Separate input to Integer numbers
Save them into Array
If this is your mean, try this code:
string str;
int arr[1000]; // I supposed 1000 is your Int Array size.
int number = 0, index = 0;
getline(cin, str); // Get a line of string
for (int i = 0 ; i < str.length() ; i++){ // Processing your str Array
if (isdigit(str[i])){
number *= 10;
number += ((int)str[i] - '0');
}
else {
arr[index++] = number;
number = 0;
}
}
arr[index] = number; // for last element of your input
// Do something you want
Try:
#include <iostream>
#include <string>
#include <vector>
#include <regex>
int main()
{
std::regex rgx("\\b\\d+\\b");
std::string line;
std::cout << "Please enter numbers separated by spaces and press enter:" << std::endl;
std::getline(std::cin, line);
std::sregex_iterator it(line.begin(), line.end(), rgx);
std::sregex_iterator end;
std::vector<int> values;
std::transform(it, end, std::back_inserter(values), [](std::smatch s){ return std::stoi(s.str()); });
for (int v : values)
std::cout << v << std::endl;
}
Use stringstream:
string str;
getline(cin, str);
stringstream ss(str);
vector<int> vec;
int Integer;
while(true)
{
ss >> Integer;
if(!ss)
break;
vec.push_back(Integer);
}
live demo
Note: You need to include following headers: <string>, <sstream>, <vector>
I am writing a code which requires me to ignore comment lines (i.e, lines beginning with a # sign) till the end of the line. I'm using linux to code in c++. For e.g: in case of adding two numbers.
xxx#ubuntu:~ $ ./add
Enter the two numbers to be added
1 #this is the first number
2 #this is the second number
result: 3
So the comment line can be anywhere. It just has to ignore the entire line and take the next value as input.
#include <iostream>
using namespace std;
int main()
{
int a,b;
cout<< "Enter the two numbers to be added:\n";
while(cin >>a >>b)
{
if (a == '#'|| b == '#')
continue;
cout << "Result: "<<a+b;
}
return 0;
}
From what you have shown, I think this might be what you want.
int main()
{
string comment;
int nr1,nr2;
// Read the first number. It should be the first one always. No comment before number!
cin >> nr1;
// See if we can read the second number Successfully. Which means it is an integer.
if(cin >> nr2) {
}
// Otherwise clear cin and read the rest of the comment line
else {
cin.clear();
getline(cin,comment);
// Now read the second number from the second line
cin >> nr2;
}
// Read the rest of second the line.
getline(cin,comment);
cout << "result: " << nr1 + nr2 << endl;
return 0;
}
Will any number of numbers based on the value you give reqd.
Will also work if the first character in a line itself is # - will ask again for that line. Will also read another line if there is no number before the `#.
#include <iostream>
#include <sstream>
#include <ctype.h>
using namespace std;
int main ()
{
const int reqd = 2;
string sno[reqd];
int no[reqd];
int got = 0;
size_t pos;
istringstream is;
cout<< "Enter "<<reqd<<" numbers to be added:\n";
while(got < reqd)
{
getline(cin, sno[got]);
if((pos = sno[got].find('#')) && isdigit(sno[got][0]))
{
is.str(sno[got]);
is>>no[got];
++got;
}
}
int sum = 0;
for(int i = 0; i < reqd; ++i)
sum+=no[i];
cout<<"Result : "<<sum;
return 0;
}