Hello all fledgling programmer here,
I am trying to create a program to identify a Palindrome. First, I enter a string and then it is reversed. Then I compare the original string to the reverse of it to determine if it is a palindrome. My problem is that the program does not ignore cases(Neven would not be considered a palindrome). I have two lines of code which are meant to make the entire string lowercase, but I am unsure of how to call those lines in the if statement. I use an if statement print a statement if the string is a palindrome
for (std::string::size_type i=0; i<abc.length(); ++i)
std::tolower(abc[i],lower);
Here is the entire code
#include <iostream>
#include <string>
#include <locale>
int main() {
std::locale lower;
std::string abc;
std::cout << "Enter Text " ;
getline(std::cin, abc);
std::cout<<"Your string is "<<abc<<std::endl;
abc=std::string(abc.rbegin(),abc.rend()); // reverse string
std::cout<<"Your reverse string is " <<abc<<std::endl;
for (std::string::size_type i=0; i<abc.length(); ++i)
std::tolower(abc[i],lower);
if(abc==std::string(abc.rbegin(),abc.rend())) {
std::cout << abc << " is a palindrome"<<std::endl;
}
else
{
std::cout<<abc<<" is not a palindrome"<<std::endl;
}
return 0;
}
I have tried to include "std::tolower(abc[i],lower);" inside the if statement but I received an error. I also tried defining it as a variable to pass that through the if statement, but that failed as well. I am unsure of how to progress.
Any help is appreciated
std::tolower() is not inplace function, it returns the lowercase ch in its return value.
Try this
abc[i] = std::tolower(abc[i],lower);
Output: After this change
Enter Text Sas
Your string is Sas
Your reverse string is saS
sas is a palindrome
std::tolower does not modify the value passed in, it returns the lowercase letter. So your line:
std::tolower(abc[i],lower);
must be changed to:
abc[i] = std::tolower(abc[i],lower);
Live On Coliru
Related
I am learning C++. I want to take multiple line string as input but I can't. I am using getline() for it but it is taking only one line input. When I press enter for writing next line it stoped taking input and print the first line.
I want to give input like the example below
Hello, I am Satyajit Roy.
I want to make a program.
I love to travel.
But it takes only the first line input.
My code:
#include <iostream>
#include <string>
using namespace std;
int main()
{
string s;
getline(cin, s);
cout << s << endl;
return 0;
}
Please help me to know how can I do that.
Thank you.
Either you write a loop to read individual lines and concatenate them to a single string, thats what this answer suggests. If you are fine with designating a specific character to signal the end of the input, you can use the getline overload that takes a delimiter as parameter:
#include <iostream>
#include <string>
int main() {
std::string s;
std::getline(std::cin,s,'x');
std::cout << s;
}
The user would have to type an x to end input, so this input
Hello, I am Satyajit Roy.
I want to make a program.
I love to travel.
x
would result in this output:
Hello, I am Satyajit Roy.
I want to make a program.
I love to travel.
Of course this won't work when the string to be entered contains x, which renders the approach rather useless.
However, instead of using a "real" character as delimiter you can use the EOF character (EOF = end of file) like this:
std::getline(std::cin, s, static_cast<char>(EOF));
Then input is terminated by whatever your terminal interprets as EOF, eg Ctrl-d in linux.
Thanks to #darcamo for enlightening me on the EOF part.
You can only read one line at a time with std::getline if you don’t provide your own delimiter. If you want to accumulate multiple lines, one at a time, you need a place to put the result. Define a second string. Read a line at a time into s with std::getline, and then append s to the result string. Like this:
std::string result;
std::string s;
while (std::getline(std::cin, s))
result += s;
You can take several lines using the code below if you know how many lines you will input.
int line=3, t;
string s, bigString;
for(int i=0 ; i<line ; i++)
{
getline(cin,s); // This is to input the sentence
bigString += s + "\n";
}
cout << bigString;
If you don't know how many lines you will input (Input from file until end of file) then you can check this.
string s;
vector<string> all;
while(getline(cin,s))
{
all.push_back(s);// This is to input the sentence
}
for(auto i:all)
{
cout << i << endl;
}
#include "stdafx.h"
#include <iostream>
#include <string>
#include <algorithm>
using namespace std;
string output;
string words;
int i;
int main()
{
cin >> words; // gets words from user
output = ""; // readys the output string
i = 0; // warms up the calculator
int size = words.size(); // size matters
while (i <= size) { // loops through each character in "words" (can't increment in the function?)
output += ":regional_indicator_" + words[i] +':'; // appends output with each letter from words plus a suffix and prefix
++i;
}
cout << output << endl; // prints the output
return 0;
}
My intentions with this code is decently clear I'd like to think. Simply take a sentence, replace all characters with that character + a suffix and prefix.
My problem is that, when ran in the debugger, I'll input "hello world" and the program will output "osss".
I have absolutely no education in C++ and am at a total loss here. Is it my ++i?
This line:
output += ":regional_indicator_" + words[i] +':'; // appends output with each letter from words plus a suffix and prefix
doesn't work. The overloading of the + operator for string concatenation only works if one of the arguments is a std::string. But you're trying to use it with a C-string literal and a char. Change that to:
output += "regional_indicator_";
output += words[i];
output += ':';
This uses the += overloading of std::string for each part, and does what you want.
Also, if you want to read a whole line, not just a single word, use:
getline(cin, words);
I am a beginner in c++ and I want to enter a string as character by character into an array , so that I can implement a reverse function .. However unlike C when the enter is hit a '\n' is not insterted in the stream.. how can I stop data from being entered ?
my code is :
#include<iostream>
#include<array>
#define SIZE 100
using namespace std;
char *reverse(char *s)
{
array<char, SIZE>b;
int c=0;
for(int i =(SIZE-1);i>=0;i--){
b[i] = s[c];
c++;
}
return s;
}
int main()
{
cout<<"Please insert a string"<<endl;
char a[SIZE];
int i=0;
do{
cin>>a[i];
i++;
}while(a[i-1]!= '\0');
reverse(a);
return 0;
}
When you read character by character, it really reads characters, and newline is considered a white-space character.
Also the array will never be terminated as a C-style string, that's not how reading characters work. That means your loop condition is wrong.
To begin with I suggest you start using std::string for your strings. You can still read character by character. To continue you need to actually check what characters you read, and end reading once you read a newline.
Lastly, your reverse function does not work. First of all the loop itself is wrong, secondly you return the pointer to the original string, not the "reversed" array.
To help you with the reading it could be done something like
std::string str;
while (true)
{
char ch;
std::cin >> ch;
if (ch == '\n')
{
break; // End loop
}
str += ch; // Append character to string
}
Do note that not much of this is really needed as shown in the answer by Stack Danny. Even my code above could be simplified while still reading one character at a time.
Since you tagged your question as C++ (and not C) why not actually solve it with the modern C++ headers (that do exactly what you want, are tested, save and work really fast (rather than own functions))?
#include <string>
#include <algorithm>
#include <iostream>
int main(){
std::string str;
std::cout << "Enter a string: ";
std::getline(std::cin, str);
std::reverse(str.begin(), str.end());
std::cout << str << std::endl;
return 0;
}
output:
Enter a string: Hello Test 4321
1234 tseT olleH
I am writing a program that extracts data from a text file and encrypts it. I am having some trouble with this. First of all there is an error at the getline(data,s[i]) part. Also the text file has two sentences but it only encrypts the second sentence. The other issue with that is It encrypts one letter at a time and outputs the sentence every time. It should output just the sentence encrypted.
#include <iostream>
#include <fstream>
#include <istream>
using namespace std;
int main(){
//Declare Variables
string s;
ifstream data;
//Uses Fstream to open text file
data.open ("/Users/MacBookPro/Desktop/data.txt");
// Use while loop to extract the data from the text file
while(!data.eof()){
getline(data,s);
cout<< s << endl;
}
//Puts the data from the text file into a string array
for(int i = 0; data.good(); i++){
getline(data, s[i]);
cout<< s <<endl;
}
// encrypts the string
if(data.is_open()){
for(int i = 0; i < s.length();i++){
s[i] += 2;
cout << s << endl;
}
}
return 0;
}
In the code below you already reach the end of the stream, and store the last line on the string s.
while(!data.eof()){
getline(data,s);
cout<< s << endl;
}
My suggestion is that you use a list of strings.
vector< string > s;
string tmp;
while(!data.eof()){
getline(data,tmp);
s.push_back(tmp);
cout<< s << endl;
}
The next step you loop through the list and do the encryption
for(i=0; i < s.size(); i++)
{
// encrypt s[i]
}
Hope this helped!
First I had to add this line to get "getline" to be recognised:
#include <string>
Then, there was indeed an error with the line:
getline(data, s[i]);
This is a compilation error, that function is expecting a stream and a string, but you pass it a stream and a char.
Changing that line for:
getline(data, s);
makes your program compile.
However it probably does not do what you want at this point, since the variable i from the for is being ignored.
I suggest that you check out some documentation on the getline function, then rethink what you want to do and try again.
You can fine some doc here:
https://msdn.microsoft.com/en-us/library/vstudio/2whx1zkx(v=vs.100).aspx
Your other concern was that it output your string many times. This is normal, since your cout statement is inside in your encryption loop.
Move it outside the loop instead, to output it only one time once the encryption loop is done.
It is important to spend the time to understand what each line of your program is doing, and why you need it to achieve your goal.
Also when doing something that we find complicated, its easier to do one small part of it at a time, make sure it works, then continue with the next part.
Good Luck :)
Create a temporary string for containing each line and an integer since we're going to find the total number of lines to create an array for all of them.
string temp = "";
int numberOfLines = 0;
Now we try to find the total number of lines
while(data.good()) {
getline(data, temp);
cout << temp << endl;
numberOfLines++;
}
Now we can create an array for all of the lines. This is a dynamic array which you can read on it for more information.
string * lines = new string[numberOfLines];
Now is the time to roll back and read encrypt all the lines. But first we have to go back to first position of file. That's why we use seekg
data.seekg(data.beg);
For each line we read, we'll put in the array and loop through each character, encrypt it and then show the whole sentence.
int i = 0;
while (data.good()) {
getline(data, lines[i]);
i++;
for (int j = 0; lines[i].size(); j++ ) {
lines[i].at(j) += 2;
}
cout << lines[i] << endl;
}
Voila!
s[i] is a character in the string (actually, a character reference), not the string object itself. string::operator[] returns a char& in the docs. See here.
Consider declaring a std::vector<string> string_array; and then use the string_array.push_back(data) member function to append strings from the file onto the vector. Use a for loop to iterate through the vector at a later time with a vector<string>::iterator or the std::vector::size function to get the length of the vector for a traditional for loop (via a call to string_array.size()). Use the square brackets to get each string from the vector (string_array[0 or 1 or etc.]).
Get characters from each string in the vector by using something like string_array[n][m] for the mth character of the nth string. Iterating over each character should be as simple as using the string::length member function to get the string length, and then another for loop.
Also, std::cout << s << std::endl is being used in the wrong places. To output each character, try std::cout << s[i] << std::endl instead, or printf("%c", s[i]), whichever you like.
I'd suggest not using an array to hold strings from the file because you don't know what the array's length will be at runtime (the file size could be unbounded), so a vector is better suited for this case.
Finally, if you need code, there's a beginner's forum post here that I think will help you out. It has a lot of code like yours, but you'll have to modify it for your purposes.
Finally, please use:
std::someCPPLibraryFunction(args);
instead of...
using namespace std;
someCPPLibraryFunction(args);
I've been doing programming challenges on coderbyte and while doing one, ran into an issue. I want to isolate a word from a string, do some checks on it and then move to another word. The code I'm going to post is supposed to take only the first word and print it out on the screen. When I run it, it doesn't print anything. I thought that maybe I did something wrong in the while loop so I did a simple test. Let's say my input is "This is a test sentence" and instead of word (in cout), I type word[0]. Then it prints "T" just fine. Can you find what the problem is?
#include <iostream>
#include <string>
using namespace std;
int Letters(string str) {
int i=0;
int len=str.length();
string word;
while(i<len){
if(isspace(str[i])){word[i]='\0'; break;}
word[i]=str[i];
i++;
}
cout<<word;
return 0;
}
int main() {
int test;
string str;
getline(cin, str);
test=Letters(str);
return 0;
}
string word;
is default constructed, which is empty initially. Inside while loop, you tried to do:
word[i] = str[i];
It means you tried to access memory that has not been allocated,resulting in undefined behavior.
Try:
word.append(str[i]);
You can use simpler way to get words from input in C++. It will help you to avoid errors in the future.
#include <iostream>
using namespace std;
int main()
{
string word;
while(cin >> word)
{
// "word" contains one word of input each time loop loops
cout << word << endl;
}
return 0;
}