How do I split an input string using getline(cin, input); to input the variable? I want to split it into a char array like this:
char[] = { // What goes here to make it read the input variable and split it into chars }
Is there any way to do this?
And what about y'all's new posts? Which one is best? Here is the caesar cipher code I need to modify to read the input variable and store its chars in a char array:
// Test Code ONLY
// Not A Commercial Program OR A Crypter
// THIS IS A TEXT CIPHERER
#include <windows.h>
#include <cstdlib>
#include <iostream>
#include <string.h>
#include <vector>
using namespace std;
int main()
{
string in;
string out;
char lower[25] = {a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t,u,v,w,x,y,z};
char upper[25] = {A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T,U,V,W,X,Y,Z};
char upcip[25] = {Z,Y,X,W,V,U,T,S,R,Q,P,O,N,M,L,K,J,I,H,G,F,E,D,C,B,A};
char locip[25] = {z,y,x,w,v,u,t,s,r,q,p,o,n,m,l,k,j,i,h,g,f,e,d,c,b,a};
cout << "Enter PlainText: ";
getline(cin, in);
// which sample goes here to read the input var char by char, then store the chars in order in a char array in your opinion?
return 0;
}
A string is already an array of chars:
for (std::string line; std::getline(std::cin, line); )
{
for (std::size_t i = 0, e = line.size(); i != e; ++i)
{
std::cout << "char[" << i << "] = '" << line[i] << "'\n";
}
}
string str;
std::getline(cin,str);
char* pArr = new char[str.size() + 1]; // add 1 for zero element which is the end of string
strcpy(pArr,str.c_str());
/*
some actions with pArr, for ex.
while(*pArr)
std::cout << *pArr; // output string on the screen
*/
// updated: release memory obtained from heap
delete [] pArr;
Related
In my main method,
int main()
{
char *words = (char *)"GETGETYETYET";
char *pattern = (char *)"GET";
return 0;
}
Instead of *words and *pattern being a predefined char set, I want to get user input, the user types in the name of a .txt file, and I want the strings in that .txt file to be stored as (char *).
How can I do this?
You don't.
Unless you want to deal with string allocations, deallocations, and ownerships, with buffer overruns and security problems, you just use std::string...
Like this:
#include <iostream>
#include <string>
int main() {
std::string a = "abcde";
std::string b;
getline(std::cin, b);
std::cout << a << ' ' << b;
return 0;
}
Suppose your strings are on the file x.txt, one per line:
#include <iostream>
#include <string>
#include <fstream>
int main() {
std::string line;
std::ifstream f("x.txt");
while( std::getline(f, line) )
std::cout << ' ' << line << '\n';
return 0;
}
The point here being that you really don't want to store things in char*...
I want to ask for word from the user and then convert the word from string to char using 'strcpy'. Then I want to determine the sum of the ascii codes for all of the letters in the word.
However, I am having difficulties. I don't understand exactly how I can do that. This is what I have been able to do so far.
#include <iostream>
#include <time.h>
#include <stdlib.h>
#include <string.h>
using namespace std;
int main()
{
string word;
cout << "Enter word: ";
getline(cin, word);
/*
char w[word];
strcpy(w,word.c_str());
int ('A');
cout<<char(65);
*/
return 0;
}
The commented part is where I have been trying to do the converting. I copied the code from a worksheet. Even if it did work, I don't know how, and what it all means.
Thanks for your help.
char w[word];
strcpy(w, word.c_str());
char w[word] is incorrect. The square brackets is for the size, which must be a constant integral expression. word is of type std::string, so this makes neither logical nor practical sense. Maybe you meant it as:
char w = word;
But that still won't work because word is a string, not a character. The correct code in this case is:
char* w = new char[word.size() + 1];
That is, you allocate the memory for w using a char*. Then you use word.size() + 1 to initialize heap-allocated memory amounting to those bytes. Don't forget for the obligatory delete[] when you're finished using w:
delete[] w;
However, note that using raw pointers and explicit new is not needed in this case. Your code can easily be cleaned up into the following:
#include <numeric>
int main ()
{
std::string word;
std::getline(std::cin, word);
int sum = std::accumulate(word.begin(), word.end(), 0); /*
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ */
std::cout << "The sum is: " << sum << std::endl;
}
You don't need to use strcpy() (or use a char * at all, for that matter), but this'll do your counting using a char pointer:
#include <iostream>
#include <string>
int main() {
std::string word;
std::cout << "Enter word: ";
std::cin >> word;
const char * cword = word.c_str();
int ascii_total = 0;
while ( *cword ) {
ascii_total += *cword++;
}
std::cout << "Sum of ASCII values of characters is: ";
std::cout << ascii_total << std::endl;
return 0;
}
Output:
paul#local:~/src/cpp/scratch$ ./asccount
Enter word: ABC
Sum of ASCII values of characters is: 198
paul#local:~/src/cpp/scratch$
If you really do want to use strcpy(), I'll leave it as an exercise to you to modify the above code.
Here's a better way to do it, just using std::string (and C++11, and obviously presuming your system uses the ASCII character set in the first place):
#include <iostream>
#include <string>
int main() {
std::string word;
std::cout << "Enter word: ";
std::cin >> word;
int ascii_total = 0;
for ( auto s : word ) {
ascii_total += s;
}
std::cout << "Sum of ASCII values of characters is: ";
std::cout << ascii_total << std::endl;
return 0;
}
The problem is that file won't be read...Apparently there's a problem with an array but I don't really know how fix this issue...I'm a beginner to C++ 'arrays' and 'strings'...
My file should read the code, then translate the file, then output the text into a new file..
#include <iostream>
#include <iomanip>
#include <string>
#include <sstream>
#include <fstream>
#include <math.h>
#include <stdio.h>
#include <string>
#include <string.h>
using namespace std;
int main()
{
// Declarations
string reply;
string inputFileName;
ifstream inputFile;
ofstream outFile;
char character;
cout << "Input file name: ";
getline(cin, inputFileName);
// Open the input file.
inputFile.open(inputFileName.c_str());
// Check the file opened successfully.
if ( ! inputFile.is_open()) {
cout << "Unable to open input file." << endl;
cout << "Press enter to continue...";
getline(cin, reply);
return 1;
}
// This section reads and echo's the file one character (byte) at a time.
while (inputFile.peek() != EOF) {
inputFile.get(character);
//cout << character;
//Don't display the file...
char cipher[sizeof(character)];
//Caesar Cipher code...
int shift;
do {
cout << "enter a value between 1-26 to encrypt the text: ";
cin >> shift;
}
while ((shift <1) || (shift >26));
int size = strlen(character);
int i=0;
for(i=0; i<size; i++)
{
cipher[i] = character[i];
if (islower(cipher[i])) {
cipher[i] = (cipher[i]-'a'+shift)%26+'a';
}
else if (isupper(cipher[i])) {
cipher[i] = (cipher[i]-'A'+shift)%26+'A';
}
}
cipher[size] = '\0';
cout << cipher << endl;
}
cout << "\nEnd of file reached\n" << endl;
// Close the input file stream
inputFile.close();
cout << "Press enter to continue...";
getline(cin, reply);
return 0;
}
To make it short: You're on c++ so just don't use the whole C stuff.
Don't use character arrays, use std::string
Don't use islower(char) but use std::islower(char,locale)
Don't use C-style arrays but std::array (compile time constant size) or std::vector (dynamic size)
You'll want to have it more like this:
#include <string>
#include <fstream>
#include <iostream>
#include <stdexcept>
#include <locale>
int main (void)
{
std::string input_filename;
std::cout << "Input file name: ";
std::getline(std::cin, input_filename);
unsigned int shift;
do
{
std::cout << "Enter a value between 1-26 to encrypt the text: ";
std::cin >> shift;
}
while ((shift == 0) || (shift > 26));
try
{
std::string filestring;
std::ifstream input(input_filename, std::ios_base::in);
if (input)
{
input.seekg(0, std::ios::end);
filestring.reserve(input.tellg());
input.seekg(0, std::ios::beg);
filestring.assign
(std::istreambuf_iterator<char>(input),
std::istreambuf_iterator<char>());
}
else
{
std::string error_string("Reading failed for: \"");
error_string.append(input_filename);
error_string.append("\"");
throw std::runtime_error(error_string);
}
std::string result;
result.reserve(filestring.size());
std::locale const loc;
for (auto character : filestring)
{
char const shifter(std::islower(character, loc) ? 'a' : 'A');
result.push_back((character-shifter+shift)%26+shifter);
}
std::cout << result << std::endl;
}
catch (std::exception & e)
{
std::cout << "Execution failed with an exception: " << std::endl;
std::cout << e.what() << std::endl;
}
}
This solution requires C++11 support. If you do not have C++11 you can replace the loop with:
size_t const N(filestring.length());
for (size_t i(0u); i<N; ++i)
{
char const shifter(std::islower(filestring[i], loc) ? 'a' : 'A');
result.push_back((filestring[i]-shifter+shift)%26+shifter);
}
From looking at your code, "character" is declared as a char which means it can only store one byte of information. Yet later on you start using it as if it was an array of characters.
You are also declare "cipher" as a char array that you manual manage like a string which is error prone. The real issue however is that you're mixing C-like code in C++. In other words, the way your code is written isn't considered idiomatic C++.
Pixelchemist already went over the important points so I'll just present a minimal refactored working example of your above code:
#include <iostream>
#include <string>
#include <fstream>
#include <stdlib.h>
using namespace std;
int main()
{
string filename;
cout << "enter input file: ";
cin >> filename;
ifstream inputFile( filename.c_str() );
string plaintext;
do
{
plaintext += inputFile.get();
}while(inputFile);
cout << plaintext << endl;
string &ciphertext = plaintext;
//Caesar Cipher code...
int shift = rand() % 26 + 1;
for(size_t i = 0; i < ciphertext.size(); ++i)
{
if (islower(ciphertext[i])) {
ciphertext[i] = (ciphertext[i] - 'a' + shift) % 26 + 'a';
}
else if (isupper(ciphertext[i])) {
ciphertext[i] = (ciphertext[i] - 'A' + shift) % 26 + 'A';
}
}
cout << ciphertext << endl;
}
You'll notice in the refactor that I've done away with char and char[] arrays altogether and replaced it with std::string. I'm also performing the cipher operation inplace on the plaintext input. This is done by making a reference alias to plaintext called ciphertext for readability. Also in my example, the shift is done randomly for prototyping but you should change it to take it as a user input instead.
You are working with a single char, thats e.g. just one letter or a number. So the whole thing with size handling is useless, because the size is always 1. You probably should use const char*. But then you can't use filestream.get() at all, because it only returns a single char (not and cstring aka const char*).
And you can use fstream.get() as condition for the loop, so you don't need to ask for the eof flag.
char my_char;
std::ifstream infstream("filename.txt");
if(!infstream.isopen())
return -1;
while(infstream.get(my_char) {
//do some stuff
}
or
std::string my_string;
std::ifstream infstream("filename.txt");
if(!infstream.isopen())
return -1;
while(infstream >> my_string) {
//do some stuff
}
for dynamic arrays in C++ use std::vector or std::list or ... one of the other STL containers, so you don't have to waste your time on memory management and using static sized arrays.
And std::string is the way to go for strings in C++. It is something similar to the STL containers, but just for char's.
I'm converting a string to char array and than back to a string and into a vector.
When I'm trying to print I'm getting this:
this
is
the
sentence iuִִ[nu#h?(h????X
and much more. This is the code:
int main(int argc, char *argv[]){
string s ="this is the sentence";
char seq[sizeof(s)];
strcpy(seq, "this is the sentence");
vector<string> vec = split(seq);
printWords(vec);
return 0;
}
And this is the func.cpp file. One function splits the char to string vector, the other is printing:
vector<string> split(char sentence[]){
vector<string> vecto;
int i=0;
int size= strlen(sentence);
while((unsigned)i< size){
string s;
char c =' ';
while(sentence[i]!=c){
s=s+sentence[i];
i+=1;
}
vecto.push_back(s);
i+=1;
}
return vecto;
}
void printWords(vector<string> words){
int i=0;
while ((unsigned)i<words.size()){
string s = words.at(i);
cout << words.at(i) << endl;
i+=1;
}
}
After understanding the answer above, try a less error-prone style, something more like this (C++11):
#include <iostream>
#include <sstream>
#include <vector>
using namespace std;
int main(){
string s{"this is the sentence"};
stringstream sStream;
sStream<<s;
string word;
vector<string> vec;
while(sStream >> word){
vec.emplace_back(word);
}
for(auto &w : vec){
cout << "a word: " << w <<endl;
}
}
One of your issues is that sizeof(s) != s.size().
Try this:
char letters = new char[s.size() + 1]; // +1 for the null terminator.
The expression sizeof(s) returns the size of the std::string object, not the quantity of characters in the string. The std::string object may be more than the string contents.
Also, try using std::string::operator[] to access individual characters in the string.
Example:
string s = "this is it";
char c = s[5]; // returns 'i' from "is".
You should also consider using the search functions of std::string, such as std::string::find_first_of.
Example:
unsigned int position = s.find_first_of(' ');
Another useful function is the substr method:
std::string word = s.substr(0, position);
How do I get a part of a string in C++? I want to know what are the elements from 0 to i.
You want to use std::string::substr. Here's an example, shamelessly copied from http://www.cplusplus.com/reference/string/string/substr/
// string::substr
#include <iostream>
#include <string>
using namespace std;
int main ()
{
string str="We think in generalities, but we live in details.";
// quoting Alfred N. Whitehead
string str2, str3;
size_t pos;
str2 = str.substr (12,12); // "generalities"
pos = str.find("live"); // position of "live" in str
str3 = str.substr (pos); // get from "live" to the end
cout << str2 << ' ' << str3 << endl;
return 0;
}
You use substr, documented here:
#include <iostream>
#include <string>
using namespace std;
int main(void) {
string a;
cout << "Enter string (5 characters or more): ";
cin >> a;
if (a.size() < 5)
cout << "Too short" << endl;
else
cout << "First 5 chars are [" << a.substr(0,5) << "]" << endl;
return 0;
}
You can also then treat it as a C-style string (non-modifiable) by using c_str, documented here.
If the string is declared as an array of characters, you can use the following approach:
char str[20];
int i;
strcpy(str, "Your String");
// Now let's get the sub-string
cin >> i;
// Do some out-of-bounds validation here if you want..
str[i + 1] = 0;
cout << str;
If you mean std::string, use substr function as Will suggested.
Assuming you're using the C++ std::string class
you can do:
std::string::size_type start = 0;
std::string::size_type length = 1; //don't use int. Use size type for portability!
std::string myStr = "hello";
std::string sub = myStr.substr(start,length);
std::cout << sub; //should print h
use:
std::string sub_of_s(s.begin(), s.begin()+i);
which create a string sub_of_s which is the first i-th the element in s.