I am fairly new to programming and have to create a program which reads the prompt: "I have 8 dollars to spend." It then needs to print out with each word on a separate line, and then if any of the strings is numeric, it needs to be divided by 2. Therefore it should end up printing out as:
I
have
4
dollars
to
spend.
I have managed to do everything, except finding the numeric value and dividing it by 2. So far I have this:
#include <iostream>
#include <string>
#include <sstream>
using namespace std;
int main()
{
string prompt;
string word;
cout << "Prompt: ";
getline(cin, prompt);
stringstream ss;
ss.str(prompt);
while (ss >> word)
{
cout << word << endl;
}
return 0;
}
After looking through various other posts, I cannot manage to get this to work. I'm assuming its an if/else statement within the while loop along the lines of, if numeric, set int num to num / 2 then cout << num << endl;, else cout << word << endl;, but I can't figure it out.
Thanks in advance.
You can use the stringstream class, which handles conversions between strings and other data types, to attempt to convert a given string to a number. If the attempt is successful, you know
The stringstream object allows you to treat a string as though it is a stream similar to cin or cout.
Incorporate this into your while loop, like so:
while (ss >> word)
{
int value = 0;
stringstream convert(word); //create a _stringstream_ from a string
//if *word* (and therefore *convert*) contains a numeric value,
//it can be read into an _int_
if(convert >> value) { //this will be false if the data in *convert* is not numeric
cout << value / 2 << endl;
}
else
cout << word << endl;
}
The strtol (C++11 version that works on std::string directly: std::stol) function is really good for testing whether a string holds a number, and if so, what the numeric value is.
Or you could continue using iostreams like you have been... try extracting a number (int or double variable), and if that fails, clear the error bit and read a string.
I dont have 50 rep so I cant comment, thats why I'm writing it as answer.
I think you can check it character by character, using Ascii value of each char, & if there are ascii values representing numbers between two spaces(two \n in this case as you've already seperated each word), then you have to divide the number by 2.
Related
I was using character arrays to get inputs from the user then display the output afterwards. However, every time I enter values with spaces in between, only the first word before the space is printed.
For instance, this is what I typed:
Customer No.: 7877 323 2332
This will be the output:
Customer No.: 7877
I already searched for possible solutions but I can't seem to find the right solution.
This is my code for reference:
#include<iostream>
using namespace std;
int main()
{
char custNum[10] = " "; // The assignment does not allow std::string
cout << "Please enter values for the following: " << endl;
cout << "Customer No.: ";
cin >> custNum;
cout << "Customer No.: " << custNum << endl;
}
Another option is to use std::basic_istream::getline to read the entire string into the buffer and then remove the spaces with a simple for loop. But when using plain-old character arrays don't skimp on buffer size. It is far better to be 1000-characters too long than one-character too short. With your input, your absolute minimum size of custNum is 14 characters (the 13 shown plus the '\0' (nul-terminating) character. (rough rule-of-thumb, take your longest estimated input and double it -- to allow for user-mistake, cat stepping on keyboard, etc...)
In you case you can simply do:
#include <iostream>
#include <cctype>
int main() {
char custNum[32] = " "; // The assignment does not allow std::string
int wrt = 0;
std::cout << "Please enter values for the following:\nCustomer No.: ";
if (std::cin.getline(custNum, 32)) { /* validate every input */
for (int rd = 0; custNum[rd]; rd++)
if (!isspace((unsigned char)custNum[rd]))
custNum[wrt++] = custNum[rd];
custNum[wrt] = 0;
std::cout << "Customer No.: " << custNum << '\n';
}
}
The two loop counters rd (read position) and wrt (write position) are simply used to loop over the original string and remove any whitespace found, nul-terminating again when the loop is left.
Example Use/Output
$ ./bin/readcustnum
Please enter values for the following:
Customer No.: 7877 323 2332
Customer No.: 78773232332
Also take a look at Why is “using namespace std;” considered bad practice? and C++: “std::endl” vs “\n”. Much easier to build good habits now than it is to break bad ones later... Look things over and let me know if you have questions.
Apart from std::getline, if you are going to use C-style strings, try the following code:
int main() {
char* str = new char[60];
scanf("%[^\n]s", str); //accepts space a a part of the string (does not give UB as it may seem initially
printf("%s", str);
return 0;
}
Also, if you absolutely need it to be a number, then use atoi
int ivar = std::atoi(str);
PS Not to forget gets (!!dangerous!!)
char* str;
gets(str);
puts(str);
cin >> int_variable will stop reading input when it reaches the first character that isn't a valid part of a number. C++ does not consider spaces part of a number, so it stops reading as soon as it encounters one.
You could use std::getline to read into a string instead, then remove the spaces from the string before converting to an integer. Or maybe in this case you don't even need the integer and can leave it as a string.
so I'm pretty new to C++ and I'm doing an assignment for my class. I ran into a problem when trying to check if an input is a string or a double/int. So I made a basic program to test it
#include <iostream>
#include <string>
using namespace std;
int main(int argc, char *argv[])
{
string hi;
double hello;
cin >> hello;
if (!cin)
{
//Strings go here
cin.clear();
cin >> hi;
cout << hi << endl;
}
else
{
cout << hello << endl;
}
cout << "Done!" << endl;
}
So it works for basically when inputting a letter (such as "j" or "a") or a number but when inputting "+" or "-" it waits for the next input then forces it through the string block, even if it is a number. However "*" or "/" are read as strings and don't cause that issue (I'm assuming since they aren't explicitly operators)
I assume I am probably missing something. Thank you
Edit: I am testing with single types at a time (such as 123, 1 , d, +) without mixing types, so there won't be any inputs that have a double and a string
As per user4581301's suggestion, I'll put in some examples input and outputs
Inputs:Outputs
"Hello":"Hello"
123:123
"/":"/"
"+" (Input after: 2):"2"
The problem
Your programme does not work exactly as intended, because it doesn't take into consideration potentially consumed but lost characters.
Here are different cases that work as expected:
abc: the first char read is not numeric, so it's not consumed and cin fails fast. The second reading reads every chars present as a string.
123abc456: the first 123 is read. When a is encountered, it is not consumed since it's not valid numeric. Further reading is stopped, but a numeric value could be read.
/123: the first char read is not numeric, so it's not consumed and cin fails. the second reading reads every char present as string.
-123 or +123: the first char is considered as a valid numeric char and is read, and then the remainder is read, still as a numeric value. Works as expected if you consider that a double ora an int can be signed. Depending on output formatting, the + might not appear with your output.
Here are the cases that do not work: if the first char is + or - but it is not followed by a valid numeric char. In this case the first char is consumed, but the next char makes the numeric input fail. The remaining chars are then read as string (except the first sign that was already consumed and is lost). Examples:
++123
+ 123 (the space ends the axtraction of the double that fails, the remainder is read as a string).
Online demo
The solution
The easiest solution is to read the input as a string, then try to convert the string.
For example:
size_t processed;
string hi;
double hello;
cin >> hi;
try {
hello = stod(hi,&processed);
cout<<"number:" <<hello;
if (processed<hi.size())
cout << " (followed by something)";
cout <<endl;
}
catch (...) // should be more precise in catching, but it's for the proof of concept
{
cout <<"string: "<< hi << endl;
}
Online demo
If you want to consider + and - as alphanumeric, it'd be easy to check if hi is non empty and hi[0] a digit before trying to do the conversion.
Alternatively, you could also do a regex check of the string to see if it matches a numeric format.
I was working on a HackerRank problem and I could not figure out why the C++ code round the double values when I am adding them and why it does not take in/print the entire string input it is given.
The code is supposed to take in an integer input (from one line), a double input (from another line), and a string input (also, from another line). Then it is supposed to print out the sum of the int input and 4, the sum of the double input and 4.0, and concatenate the string "HackerRank" to the beginning of the input string.
Here's the code I have:
#include <iostream>
#include <iomanip>
#include <limits>
int main(){
int i = 4;
double d = 4.0;
string s = "HackerRank";
// Declare second integer, double, and String variables.
// Read and save an integer, double, and String to your variables.
// Note: If you have trouble reading the entire string, please go back and review the Tutorial closely.
// Print the sum of both integer variables on a new line.
// Print the sum of the double variables on a new line.
// Concatenate and print the String variables on a new line
// The 's' variable above should be printed first.
int a;
double b;
string c;
cin >> a;
cin >> b;
cin >> c;
a = a + i;
b = b + d;
cout << a << endl;
cout << b << endl;
cout << "" + s + c;
return 0;
}
For the following input:
12
4.0
is the best place to learn and practice coding!
I got the output:
16
8
HackerRank is
When this is the expected output:
16
8.0
HackerRank is the best place to learn and practice coding!
The answer to your 2 questions:
Firstly, when you add a value of type int to a value of type float/string, the result will be of type int. This explains why you the output is 8 and not 8.0. This same rule applies to multiplication, division, and subtraction. Whenever an int is operated on by a float/double value or vice versa, the result is always of type int. Therefore, you should change the initialization of your d value to:
double d = 4.0; // Or float d = 4.0
By the way, you cannot add a decimal point to a value of type int and expect it to be a floating point/double value. The data type of the variable that stores the value must be defined/initialized with a certain data type.
Secondly, your code does not print the desired string as you are using the wrong function to get the string as input from the user. While cin is the norm to be used in input, it does not work so well with variables of type "string". The reason for this is because cin only accepts one word; one continuous int, floating point value, char, etc..., and it cannot accept an entire sentence with spaces in between because it just stops reading after it sees a space; that's the rules of cin. To bypass this problem, you'll need another function, and that is
getline(cin, variable_to_store_data);
instead of doing:
cin >> c;
Do this:
getline(cin, c);
This way, the entire sentence you inputted will be stored in the variable and not just the first word of the sentence. The getline does not ignore the words in a sentence that come after the first one; it reads all of the user input till the point he/she hits Enter, and it then stores the entire value in the variable (that's the second parameter).
By the way, if you want to output multiple things in one cout line, then do it using the following template:
cin << a << ... << z << endl; // endl is optional; depends on your needs
Avoid using the method you used above:
cout << "" + s + c;
Do it this way:
cout << "" << s << c; // Why do you have "" at the begninning? That prints nothing. You can take that off also.
On a side note, getline() also has a lot of other functions, such as reading lines from a file. Read more about it online; there are lots of resources available.
Hope this answers your question.
EDIT: To make the program work, you'll actually have to add another line to ignore the enter hit at the end of the cin >> b; command, because that saves as the string in c. Therefore, do this:
cin.ignore (std::numeric_limits<std::streamsize>::max(), '\n');
getline(cin, c);
The line I just added ignores the newline character hit at the end of the cin >> b command. This way, the compiler goes on to ask the user for the string to be stored in c. I've tried this code, and it works as it should.
Another thing, change your output statement to;
cout << "" << s << " " << c << "." << endl;
This makes the string easier to read, and it adds a space between variable s and variable c during output. Hope this helps!
This code will work...
#include<iostream>
#include<string.h>
using namespace std;
int main()
{
int i = 4;
double d = 4.0;
string s = "HackerRank ";
int i2;
double d2;
string s2;
cin>>i2;
cin>>d2;
cin.ignore();
getline(cin, s2);
cout<<i2+i<<endl;
cout.precision(1);
cout << fixed << d+d2 << endl;
cout<<s+s2;
return 0;
}
You can use the function 'getline' to realize it.
And the following example is well done on VS2013.
#include <string>
#include <iostream>
using namespace std;
int main(){
string c;
getline(cin, c); // is there anybody ?
cout << "Hello, " + c; // Hello, is there anybody ?
system("pause");
return 1;
}
cin>>b;
use cin.ignore();
and then getline(cin, string_name);
This will read the complete string.
This may be a total beginner's question, but I have yet to find an answer that works for me.
Currently, I'm writing a program for a class that takes in a user's input (which can be one or more numbers separated by spaces), then determines whether the number is prime, perfect, or neither. If the number is perfect, then it will display the divisors.
Thus far, I've already written the code for the prime, perfect, and listing the divisors. I'm stuck on the input portion of my program. I don't know how to get the input that's separated by spaces to go through my loops one at a time.
This is my current program:
cout<<"Enter a number, or numbers separated by a space, between 1 and 1000."<<endl;
cin>>num;
while (divisor<=num)
if(num%divisor==0)
{
cout<<divisor<<endl;
total=total+divisor;
divisor++;
}
else divisor++;
if(total==num*2)
cout<<"The number you entered is perfect!"<<endl;
else cout<<"The number you entered is not perfect!"<<endl;
if(num==2||num==3||num==5||num==7)
cout<<"The number you entered is prime!"<<endl;
else if(num%2==0||num%3==0||num%5==0||num%7==0)
cout<<"The number you entered is not prime!"<<endl;
else cout<<"The number you entered is prime!"<<endl;
return 0;
It works, but only for a single number. If anyone could help me to get it to be able to read multiple inputs separated by spaces, it'd be greatly appreciated. Also, just a side note, I do not know how many numbers will be entered, so I can't just make a variable for each one. It will be a random amount of numbers.
Thanks!
By default, cin reads from the input discarding any spaces. So, all you have to do is to use a do while loop to read the input more than one time:
do {
cout<<"Enter a number, or numbers separated by a space, between 1 and 1000."<<endl;
cin >> num;
// reset your variables
// your function stuff (calculations)
}
while (true); // or some condition
I would recommend reading in the line into a string, then splitting it based on the spaces. For this, you can use the getline(...) function. The trick is having a dynamic sized data structure to hold the strings once it's split. Probably the easiest to use would be a vector.
#include <string>
#include <vector>
...
string rawInput;
vector<String> numbers;
while( getline( cin, rawInput, ' ' ) )
{
numbers.push_back(rawInput);
}
So say the input looks like this:
Enter a number, or numbers separated by a space, between 1 and 1000.
10 5 20 1 200 7
You will now have a vector, numbers, that contains the elements: {"10","5","20","1","200","7"}.
Note that these are still strings, so not useful in arithmetic. To convert them to integers, we use a combination of the STL function, atoi(...), and because atoi requires a c-string instead of a c++ style string, we use the string class' c_str() member function.
while(!numbers.empty())
{
string temp = numbers.pop_back();//removes the last element from the string
num = atoi( temp.c_str() ); //re-used your 'num' variable from your code
...//do stuff
}
Now there's some problems with this code. Yes, it runs, but it is kind of clunky, and it puts the numbers out in reverse order. Lets re-write it so that it is a little more compact:
#include <string>
...
string rawInput;
cout << "Enter a number, or numbers separated by a space, between 1 and 1000." << endl;
while( getline( cin, rawInput, ' ') )
{
num = atoi( rawInput.c_str() );
...//do your stuff
}
There's still lots of room for improvement with error handling (right now if you enter a non-number the program will crash), and there's infinitely more ways to actually handle the input to get it in a usable number form (the joys of programming!), but that should give you a comprehensive start. :)
Note: I had the reference pages as links, but I cannot post more than two since I have less than 15 posts :/
Edit:
I was a little bit wrong about the atoi behavior; I confused it with Java's string->Integer conversions which throw a Not-A-Number exception when given a string that isn't a number, and then crashes the program if the exception isn't handled. atoi(), on the other hand, returns 0, which is not as helpful because what if 0 is the number they entered? Let's make use of the isdigit(...) function. An important thing to note here is that c++ style strings can be accessed like an array, meaning rawInput[0] is the first character in the string all the way up to rawInput[length - 1].
#include <string>
#include <ctype.h>
...
string rawInput;
cout << "Enter a number, or numbers separated by a space, between 1 and 1000." << endl;
while( getline( cin, rawInput, ' ') )
{
bool isNum = true;
for(int i = 0; i < rawInput.length() && isNum; ++i)
{
isNum = isdigit( rawInput[i]);
}
if(isNum)
{
num = atoi( rawInput.c_str() );
...//do your stuff
}
else
cout << rawInput << " is not a number!" << endl;
}
The boolean (true/false or 1/0 respectively) is used as a flag for the for-loop, which steps through each character in the string and checks to see if it is a 0-9 digit. If any character in the string is not a digit, the loop will break during it's next execution when it gets to the condition "&& isNum" (assuming you've covered loops already). Then after the loop, isNum is used to determine whether to do your stuff, or to print the error message.
You'll want to:
Read in an entire line from the console
Tokenize the line, splitting along spaces.
Place those split pieces into an array or list
Step through that array/list, performing your prime/perfect/etc tests.
What has your class covered along these lines so far?
int main() {
int sum = 0;
cout << "enter number" << endl;
int i = 0;
while (true) {
cin >> i;
sum += i;
//cout << i << endl;
if (cin.peek() == '\n') {
break;
}
}
cout << "result: " << sum << endl;
return 0;
}
I think this code works, you may enter any int numbers and spaces, it will calculate the sum of input ints
std::vector<int> num{};
int buf;
do{
std::cin >> buf;
num.push_back(buf);
}while(std::cin.peek() == ' ');
In C language you can to it using scanf like this:
scanf('%d %d',&a,&b);
I've come this far without asking for help, but I've got a problem that I can't seem to fix. I like cryptology, so now that I am learning C++, I want to make programs to encrypt and decrypt strings. I read that the best way is to convert the text to ASCII and go from there, so here is a simple program I made in C++ to try and convert a char variable to ASCII:
#include <iostream>
#include <string>
#include <math.h>
using namespace std;
int main()
{
char strString[1000];
cout<<"Enter you message:"<<endl;
cin>>strString[1000];
string strEncrypt;
int a = 0;
while (strString != '\0')
{
int b = (int)strString[a];
strEncrypt.at(a) = b; //This is where I'm getting an error.
a++;
}
cout<<"Encrypted message:"<<endl;
cout<<strEncrypt<<endl;
}
So, I've tried all 3 things I know to do to troubleshoot (Google, check for missing simicolons, and make sure I'm doing == not =, but this is just something I don't know how to do, not something I'm forgetting (I hope). So, any help would great!
You don't have to change the characters to ASCII they already are. Chars are basically the same as integers in memory.
Now to your question; . If you want to set a character in a string you can do that like this
string[index] = b;
Another thing to be careful for in your code. You are using cin to read the string from the user. This will not let you read messages that have spaces in them and will only read the first word. For example, if the user enters "Love Crypto" cin will only read "Love" and "Crypto" will be ignored. To get the entire line, use getline instead.
As for looping over characters in a string, it's better to do it as follows:
for(int i = 0; i < strString.length(); i++)
{
strString[i] = bla;
}
Again, you're code isn't actually doing anything. It is only reading a letter and then storing a "letter" in another string.
string::at() throws exception if the index passed to at() is out of range. So, if you are getting runtime error then it's expected. Because, your string strEncrypt is initialized to "" and thus the size is 0.
You may try
strEncrypt.reserve(strlen(strString));
Easiest way to actually make the code you have work is change this line strEncrypt.at(a) = b; to this strEncrypt += b; Which will add the characters to the empty string strEncrypt.
Your code doesn't make much sense though as char types are already ascii. You'll have to explain more about what kind of encrypting you are trying to do and maybe we can point you in the right direction.
EDIT: After thinking about what you're trying to do a bit more based on the code you have it seems like you want to print the numeric ascii value of characters. You can do that with just a cast like this:
string input;
cout << "Enter you message:" << endl;
// handle spaces in the message
getline(cin, input);
cout << "String chars as ascii values:" << endl;
cout << "Char: " << "ASCII Code:" << endl;
for (int i = 0; i < input.length(); ++i)
{
// casting the char to an int with (int) will print the ascii code
cout << input[i] << " " << (int)input[i] << endl;
}
On top of the fact that your input is already in ASCII, keep in mind that doing cin >> strString[1000] doesn't limit the input captured to the length of your buffer unless you specifically specify the number of characters to capture for the stream object using setw() or setting it's ios_base::width data member. So your method right now risks buffer overflows.
Secondly, the form of cin >> that you're using will not capture the entire line of input. Instead it will stop at the first white-space or any other delimiting character (or end-of-file if that is reached first). In your case, if you are entering a line like "Hello World", then the syntax you're using will only capture "Hello" and drop "World".
A much better idea would be to use the getline() function with a std::string object if you are wanting to capture a line of input to a string and remove the delimiting newline character without risking buffer overflows ... for instance:
string strString;
getline(cin, strString);
Apart from advises given, when receiving this kind of run-time errors use Cppcheck utility.
It will give you the answer: "Message: Array 'strString[1000]' index 1000 out of bounds".