I am implementing the ALV tree, and I need to read input from the command line.
An example of the command is as follows:
insert “NAME_ANYTHING_IN_QUOTES_$” ID
where NAME_ANYTHING_IN_QUOTES_$ is the data being stored in the AVL tree, and ID is used to decide if the info will be stored in the left subtree or right subtree.
Code snipet is as follows:
if (comand == "insert")
{
int ID = 0;
string Name;
cin >> Name;
cin >> ID;
root = insertInfo(root, Name, ID);
}
I can not figure out how to scan in the substring that is between two double-quotes.
Thanks.
Use std::quoted:
std::string name;
std::cin >> std::quoted(name);
I found the answer....😊
string name,ID,concat;
getline(cin, concat);
for(int i =0; i< concat.length();i++){
if(!isdigit(concat[i])&& concat[i] != 34){
name += concat[i];
}
if(isdigit(concat[i])){
ID += concat[i];
}
}
cout<<"name is ->"<<name<<endl;
cout<<"ID is ->"<<ID<<endl;
I'm just adding to HolyBlackCat's answer above.
Here's code that works:
#include <iostream>
#include <iomanip>
using namespace std;
int main(int argc, const char** argv)
{
//if (comand == "insert")
{
int ID = 0;
string Name;
cin >> std::quoted(Name);
cin >> ID;
cout << "name is " << Name << " and ID is " << ID << endl;
//root = insertInfo(root, Name, ID);
}
}
When input is "MyName_$" 34
I get
name is MyName_$ and ID is 34
So, HolyBlackCat's solution works. Show us your code and input.
On second thought, those strange open and close braces may depend on the font, etc. The std::quoted should have worked for you, but it you say it doesnt. Let us know what env and compiler you are using. If you're sure they're always there, you can just delete the first and last char in that string as in:
#include <iostream>
#include <string>
using namespace std;
int main(int argc, const char** argv)
{
//if (comand == "insert")
{
int ID = 0;
string Name;
cin >> Name;
Name.erase(0, 1);
Name.erase(Name.length() - 1, 1);
cin >> ID;
cout << "name is " << Name << " and ID is " << ID << endl;
//root = insertInfo(root, Name, ID);
}
}
Related
How can I ignore the first line of the text file and start at the second line when I called it in the code? I was wondering how. Also, how can I sort the file according to first name, last name and grade? I just have the first name sorted but not the last name and grade accordingly. If you have any idea, I hope you can share it with me. Thanks for the help! Here's my code:
#include <iostream>
#include <fstream>
using namespace std;
struct studentRecord{
string lastname;
string firstname;
string grade;
};
int main(){
ifstream ifs("student-file.txt");
string lastname, firstname, grade, key;
studentRecord records[20];
if(ifs.fail()) {
cout << "Error opening student records file" <<endl;
exit(1);
}
int i = 0;
while(! ifs.eof()){
ifs >> lastname >> firstname >> grade;
records[i].lastname = lastname;
records[i].firstname = firstname;
records[i].grade = grade;
i++;
}
for (int a = 1, b = 0; a < 20; a++) {
key = records[a].firstname ;
b = a-1;
while (b >= 0 && records[b].firstname > key) {
records[b+1].firstname = records[b].firstname;
b--;
}
records[b+1].firstname = key;
}
for (int k = 0; k < 20; k++) {
cout << "\n\t" << records[k].firstname << "\t"<< records[k].lastname << "\t" << records[k].grade;
}
}
When I saw this post it reminded me of a similar task completed at uni. I have rewritten your code to perform the same task but using classes instead of structs. I have also included a way to sort the vector by using the function here.
I have included the "ignore first line" method #Scheff's Cat mentioned.
Here it is:
#include <iostream>
#include <fstream>
#include <sstream>
#include <limits>
#include <string>
#include <vector>
using namespace std;
class studentrecord{
string firstname, lastname, grade;
public:
studentrecord(string firstname, string lastname, string grade){
this -> firstname = firstname;
this -> lastname = lastname;
this -> grade = grade;
}
friend ostream& operator<<(ostream& os, const studentrecord& studentrecord) {
os << "\n\t" << studentrecord.firstname << "\t" << studentrecord.lastname << "\t" << studentrecord.grade;
return os;
}
};
void displayRecords(vector <studentrecord*> records){
for(int i = 0; i < records.size(); i++){
cout << *records[i];
}
}
int main(){
//read in file
ifstream infile;
infile.open("student-file.txt");
infile.ignore(std::numeric_limits<std::streamsize>::max(), '\n');
if (!infile.is_open()){
cout << "Error opening student records file" <<endl;
exit(1);
}
vector <studentrecord*> records;
string firstname, lastname, grade;
while (infile >> firstname >> lastname >> grade;) {
records.push_back(new studentrecord(firstname, lastname, grade));
}
displayRecords(records);
return 0;
}
To sort the vector so that it prints in order of either first name, last name or grade I used the following functions:
bool sortfirstname(studentrecord* A, studentrecord* B) {
return (A->getfirstname() < B->getfirstname());
}
bool sortlastname(studentrecord* A, studentrecord* B) {
return (A->getlastname() < B->getlastname());
}
bool sortgrade(studentrecord* A, studentrecord* B) {
return (A->getgrade() < B->getgrade());
}
sort(records.begin(), records.end(), (sortfirstname));
sort(records.begin(), records.end(), sortlastname);
sort(records.begin(), records.end(), sortgrade);
If you wanted to sort by first name you would call the sort(records.begin(), records.end(), (sortfirstname)); function and then the displayrecords() function.
The advantage of using classes stored in vectors is that you don't have to state the size of the vector containing the details about students since you can keep adding information to the end of the vector using the vector.push_back() function. It also makes sorting the data contained easier.
If anything isn't clear, let me know and I can give you a hand.
I just started learning C++ and I'm currently following a tutorial on YouTube.
I thought it was fun to make a very simple 'access' program. If I type in my name it says, "Welcome!" If I type in another name it says, "access denied". It worked perfectly fine, but then I wanted the program to say "Welcome!" to two different names. So, I wanted to add a second name in the string, but I couldn't figure out how to do that. I googled a lot but I couldn't find anything. In the end, I came to string name = ("Joe", "Sean");, but here, it was only valid for Sean. I just can't figure out how to put multiple names in one string and make them both work. I hope you can help me, here is my code:
#include <iostream>
#include <cmath>
#include <string>
using namespace std;
int main()
{
string name = ("Joe", "Sean");
string input;
cout << "What is your name?\nMy name is: ";
cin >> input;
if(input == name){
cout << "Welcome, "<< input <<"! ";
} else {
cout << "Access denied";
}
return 0;
}
This is a way to do it using a vector of strings, so you can adapt easily with more names :
#include <iostream>
#include <vector>
using namespace std;
void printMessage(string message)
{
std::cout << message << std::endl;
}
int main()
{
vector<string> names{"Joe", "Sean", "Paul"};
string input;
cout << "What is your name? " << endl;
cin >> input;
for (string name : names)
{
if (name == input)
{
printMessage("Welcome!");
return 0;
}
}
printMessage("Access Denied!");
return 0;
}
The problem is in the string variable "name". You need an array of strings, not a single string.
This is an example implementation:
#include <iostream>
#include <cmath>
#include <string>
using namespace std;
int main()
{
string names[] = {"Joe", "Sean"};
string input;
cout << "What is your name?\nMy name is: ";
cin >> input;
for (int i = 0; i < end(names) - begin(names); i++) {
if(input == names[i]){
cout << "Welcome, "<< input <<"! " << endl;
return 0;
}
}
cout << "Access denied" << endl;
return 0;
}
You encountered some quirky features of C++ in the approach you are using to initialize your string variable:
string s1 = ("Joe"); // creates a string "Joe"
string s2 = ("Joe", "Sean"); // creates 2 strings, "Joe" and "Sean", and the variable s2 stores only the latter!
For more details on the different methods for initializing variables there has been an interesting discussion in this previous question.
This program reads an SSN from the user and checks if it matches an SSN in a text file provided. Tried switching the array to a vector and it didnt work. Tried putting the array in the structure function and using info:: but nothing seems to work. I know this is pretty basic but I cant get it, thanks.
#include <iostream>
#include <fstream>
using namespace std;
int main(int argc, char* argv[]){
struct info{
string SSN;
string firstName;
string lastName;
};
string list[1000];
string userSSN;
char x;
fstream input(argv[1]);
int i = 0;
while(!input.eof()){
input >> list.x[i] >> list.SSN[i] >> list.firstName[i] >> list.lastName[i];
i++;
}
input.close();
cout << "Input a SSN:" << endl;
cin >> userSSN >> endl;
for(int k = 0; k < i; k++){
if(userSSN.compare(list.SSN[k]) == 0){
cout << "Found at location " << k << endl;
}
}
}
list is just an array of 1000 std::strings. It looks like you need it to be of type info. Even that won't solve your problems as info has no member named x. After that, to access a member of info in an array would be like
list[i].SSN
not
list.SSN[i]
There are so many things wrong with this code that I don't know where to start. Let's see:
Using using namespace std; is almost always a bad idea, and if you have an identifier list, then it's even worse because it conflicts with std::list.
Using std::string without #include <string> is not guaranteed to work. It may work if you include some other standard header, but don't rely on it.
Your variable x is unused.
string list[1000]; should probably be info list[1000];.
list.SSN[i] et al should probably be changed to list[i].SSN.
list.x[i] does not make sense at all and can probably be removed. (Or you meant to read into the otherwise unused x to skip parts of the file.)
You cannot read from std::cin into std::endl. Remove std::endl from that line.
Using std::string's compare function is pretty strange here, just use ==.
The issues in your code were already pointed out in other's answers. I'll show you a "working" example:
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
using std::string;
using std::vector;
using std::cout;
using std::cin;
struct info {
char x; // You were reading that from the file so I added it
string SSN;
string firstName;
string lastName;
friend std::istream &operator>>( std::istream &is, info &i ) {
// maybe you should check data input somehow...
is >> i.x >> i.SSN >> i.firstName >> i.lastName;
return is;
}
};
int main(int argc, char* argv[]) {
// check if a file name has been passed as a parameter
string file_name;
if ( argc < 2 ) {
cout << "Please, enter the input file name:\n";
cin >> file_name;
}
else
file_name = argv[1];
std::ifstream input(file_name);
if ( !input ) {
std::cerr << "Error. Unable to open file: " << file_name << '\n';
exit(-1);
}
// Just use a vector to store all the structs
vector<info> my_list;
info temp_info;
while( input >> temp_info ) {
my_list.push_back(temp_info);
}
input.close();
cout << "Input a SSN: ";
string userSSN;
cin >> userSSN;
// That's not cheap. You may want to change the container or sort it
for ( int k = 0; k < my_list.size(); k++ ) {
if ( userSSN == my_list[k].SSN ) {
cout << "Found at location " << k << '\n';
}
}
return 0;
}
I want to read from a file two things, the full name (first name and last name)
and age. After that I want to store them in an array then print the data.
However, when I try to reading the first record is read find, but the other two are not.
Please tell me what am I missing.
Thank you.
The content of the file is:
sampleFirst1 sampleLast1
30
sampleFirst2 sampleLast2
25
sampleFirst3 sampleLast3
40
The Output is:
Name: sampleFirst1 Age: 30
Name: Age: 30
Name: Age: 30
Here's my Code:
#include "Person.h"
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
ifstream inputFile("data.txt", ios::in);
string full_name;
int age = 0;
int i = 0;
Person personArray[3];
while (i < 3)
{
getline(inputFile, full_name);
personArray[i].set_name(full_name);
inputFile >> age;
personArray[i].set_age(age);
++i;
}
inputFile.close();
printData(personArray, 3);
cout << endl;
return 0;
}
You should not mix getline and the >> operator in that way. Prefer a simpler code like this one :
#include <iostream>
#include <fstream>
#include <array>
#include <string>
using namespace std;
struct Person {
std::string name;
int age;
void set_name(std::string const& i_name) { name = i_name; }
void set_age(int i_age) { age = i_age; }
};
int main()
{
ifstream inputFile("data.txt", ios::in);
std::string first;
std::string last;
int age = 0;
int i = 0;
std::array<Person,3> personArray;
while (i < personArray.size()) {
inputFile >> first >> last >> age;
personArray[i].set_name(first + " " + last);
personArray[i].set_age(age);
++i;
}
inputFile.close();
for(Person const& person : personArray) {
std::cout << "Name: " << person.name << " Age: " << person.age << "\n";
}
std::cout << std::flush;
return 0;
}
Or use only getline and a istringstream to pase the age if you dont want to pay the string concatenation extra cost for the full name.
A lot could be said of the parsing method but that is not the point here.
my text is something like this
55<space>The User Input Sentence;
i got the 55 out via the code below and assigned that to a int variable via atoi
std::string stringKey = userInput.substr(0, 2);
but how to get the rest of the string and assign it to a string variable ????the code below
this is the complete code (haven't finished it yet)
#include <iostream>
#include <string>
#include <algorithm>
#include <iomanip>
#include <cmath>
using namespace std;
//FUnction Prototypes
string encrypt(string, int);
string decrypt(string source, int key);
int main(int argc, char *argv[])
{
string source;
string userInput;
int key;
int choice;
cout << "To encode a message type 1, to decode a message type 2: ";
cin >> choice;
if (choice == 1)
{
cout << "Enter the message to encode: ";
cin >> userInput;
std::string stringKey = userInput.substr(0, 2);
key = atoi(stringKey.c_str());
std::string source = userInput.substr(3);
encrypt(source, key);
}
/*decrypt(source, key);
cout << "Source: ";
getline(cin, source);
cout << "Key: ";
cin >> key;
cout << "Encrypted: " << decrypt(source, key) << endl;*/
system("pause");
}
string encrypt(string source, int key)
{
string Crypted = source;
for (int Current = 0; Current < source.length(); Current++)
Crypted[Current] = ((Crypted[Current] + key) - 32) % 95 + 32;
return Crypted;
}
string decrypt(string source, int key)
{
string Crypted = source;
for (int Current = 0; Current < source.length(); Current++)
Crypted[Current] = ((Crypted[Current] - key) - 32 + 3 * 95) % 95 + 32;
return Crypted;
}
Same way as you got first part. Check out std::string substr
string second = userInput.substr(3);
----------------EDIT------------------
If you give 55<space>The User Input Sentence as input, only first string will be read.
Use getline method to read entire input including spaces