This question already has answers here:
Replace part of a string with another string
(17 answers)
Closed 2 years ago.
I started learning C ++ and my task is to replace some characters in the text. Something similar to the template Here are some examples:
<h1>Title</h1>$ js $<p>text...</p>
result:
<h1>Title</h1> </script>alert(1)</script> <p>text...</p>
I tried to do it with this code, but nothing worked:
#include <iostream>
#include <string>
using namespace std;
int main(){
string text = "<h1>Title</h1>$ js $<p>text...</p>";
string js_code = " </script>alert(1)</script> ";
string result = text.replace(text.find("$ js $"), js_code.length(), js_code);
cout << result << endl;
return 0;
}
result:
<h1>Title</h1> </script>alert(1)</script>
The text was inserted into the line, but everything after this text disappeared. Also, sometimes I will use Russian characters, and they are in UTF-8 encoding. 1 Symbol weighs more.
The second parameter of std::string::replace(size_type pos, size_type count, const basic_string& str); is the
length of the substring that is going to be replaced
e.g. how many characters should be removed after pos and before inserting str. You want to replace just 6 characters. Your code should look like this:
std::string pattern = "$ js $";
std::string result = text.replace(text.find(pattern), pattern.length(), js_code);
On another note you should check if find returns a valid index before using it.
Related
I'm trying to learn strings and I've figured out how to replace as well as insert into an existing string. I have 3 strings at the moment which I've declared as constants, I've merged them into one string variable which puts them all one after eachother.
I've also changed every single occurance of "Hi" to "Bye" in those strings. My 3 strings bundled into a single one are as following:
"Hi! My name is xxxx! I would like to be on my own but I don't know how to, could you help me?"
I want it to display as:
Hi!
My name is xxxx!
I would like to be on my own but I don't know how to, could you help me?
As soon as a puncutation occurs I'd like to insert a line break "\n", using replace works but that means the punctuation will disappear, using insert will first insert the line break before the punctuation, and it won't continue to the next one which results in:
"Hi!
My name is xxxx! I would like to be on my own but I don't know how to, could you help me?"
I changed the code to only include dots to simplify it, once solved the same solution can be applied to any other part such as question marks or exclamation marks.
Any tips on how to fix this?
#include <iostream>
#include <string>
using namespace std;
string const Text0 = "Hi.";
string const Text1 = "My name is xxxx.";
string const Text2 = "I would like to be on my own but I don't know how to, could you help me.";
string const Text3 = "I would, but I don't know how to.";
string text = Text0 + Text1 + Text2 + Text3;
int main() {
while (text.find("I") != string::npos) {
text.replace(text.find("I"), 1, "J");
}
while (text.find("like") != string::npos) {
text.replace(text.find("like"), 4, "milk");
}
text.insert(text.find("."), "\n");
cout << text;
return 0;
}
You can create your own short function that will add newline after every punctuation sign.
For example:
void addNewLines(std::string *text)
{
for (int i = 0; i < text->length(); i++)
{
if ((*text)[i] == '!' || (*text)[i] == '?' || (*text)[i] == '.')
{
(*text)[i + 1] = '\n';
}
}
}
As you can see in this piece of code, in the for loop you are going from the first to the last character of the string, and after every punctuation sign you replace empty space with \n character.
I'm using pointers here to prevent copying of the string to the function, in case it is a huge string, but you could do it without pointers, that way syntax is a little bit cleaner.
This question already has answers here:
Read whole ASCII file into C++ std::string [duplicate]
(9 answers)
Closed 3 years ago.
I am trying this following code in cpp
#include <iostream>
#include <string>
void Strlength(const string& s) {
cout << s.length() << endl;
}
int main() {
string s;
cin >> s;
cout << s.length() << endl;
Strlength(s);
return 0;
}
The string which I am giving as input is 100,000 characters long and is like "xxxxxxx...xxxxabcde"(fill the ... with remaining x)
This gives me the output as
4095
4095
I am expecting the output to be 100000. what am I doing wrong?
This relates to one of the hackerrank problem (Test case 10): String Similarity
Assuming you describe the input correctly, that is it is one single "word", then the issue is not in your code. The issue must be in the environment which runs the code. It has some kind of mechanism to feed the standard input to your program. Either that has a limitation on total input length, or it has a limitation of line length. 4 kilobytes is 4096 bytes, so perhaps your input is limited by that: 4095 chars of the word plus a newline character (or terminating 0 byte of string, or whatever).
If you are running this under some kind of web interface in browser, the problem could even be, that the input field in the web page has that limitation.
If you need to dig into this, try to read char by char and see what you get, how many chars and how many newlines. Also examine cin.fail(), cin.eof(), cin.bad() and cin.good(). For the question code, you should expect failbit to be false, and eofbit might be true oe false depending on how the input was truncated.
I use this function to remove duplicate words in a file
But I need it to remove duplicate expressions instead
for example What the function is currently doing
If I have the expression
"Hello World"
"beautiful world"
The function will remove the word "world" from both expressions
And I need this function to replace the entire expression only if it is found more than once in the file
for example
If I have the expressions
"Hello World"
"Hello World"
"beautiful world"
"beautiful world"
The function will remove the expression "Hello world" and "beautiful world" and leave only one from each of them but it will not touch the word "world" because the function will treat everything that is within the quotes as one word
This is the code I use now
#include <string>
#include <sstream>
#include <iostream>
#include <unordered_set>
void Remove_Duplicate_Words(string str)
{
ofstream Write_to_file{ "test.txt" };
// Used to split string around spaces.
istringstream ss(str);
// To store individual visited words
unordered_set<string> hsh;
// Traverse through all words
do
{
string word;
ss >> word;
// If current word is not seen before.
while (hsh.find(word) == hsh.end()) {
cout << word << '\n';
Write_to_file << word << endl; // write to outfile
hsh.insert(word);
}
} while (ss);
}
int main()
{
ifstream Read_from_file{ "test.txt" };
string file_content{ ist {Read_from_file}, ist{} };
Remove_Duplicate_Words(file_content);
return 0;
}
How do I remove duplicate expressions instead of duplicate words?
Unfortunately my knowledge on this subject is very basic and usually what I do is try all kinds of things until I succeed. I tried to do it here too and I just can not figure out how to do it
Any help would be greatly appreciated
Requires a little bit of String parsing.
Your example works by reading tokens, which are similar to words (but not exactly). For your problem, the token becomes word OR quoted string. The more complex your definition of tokens, the harder the problem becomes. Try starting by thinking of tokens as either words or quoted strings on the same line. A quoted string across lines might be a little more complex.
Here's a similar SO question to get you started: Reading quoted string in c++. You need to do something similar, but instead of having set positions, your quoted string can occur anywhere in the line. So you read tokens something like this:
Read next word token (as you're doing now)
If last read token is quote character ("), read till next (") as a single token
Check on the set and output token only if it isn't already there (if token is quoted, don't forget to output the quotes)
Insert token into set.
Repeat till EOF
Hope that helps
Using the C++ Standard Template Library function regex_replace(), how do I remove non-numeric characters from a std::string and return a std::string?
This question is not a duplicate of question
747735
because that question requests how to use TR1/regex, and I'm
requesting how to use standard STL regex, and because the answer given
is merely some very complex documentation links. The C++ regex
documentation is extremely hard to understand and poorly documented,
in my opinion, so even if a question pointed out the standard C++
regex_replace
documentation,
it still wouldn't be very useful to new coders.
// assume #include <regex> and <string>
std::string sInput = R"(AA #-0233 338982-FFB /ADR1 2)";
std::string sOutput = std::regex_replace(sInput, std::regex(R"([\D])"), "");
// sOutput now contains only numbers
Note that the R"..." part means raw string literal and does not evaluate escape codes like a C or C++ string would. This is very important when doing regular expressions and makes your life easier.
Here's a handy list of single-character regular expression raw literal strings for your std::regex() to use for replacement scenarios:
R"([^A-Za-z0-9])" or R"([^A-Za-z\d])" = select non-alphabetic and non-numeric
R"([A-Za-z0-9])" or R"([A-Za-z\d])" = select alphanumeric
R"([0-9])" or R"([\d])" = select numeric
R"([^0-9])" or R"([^\d])" or R"([\D])" = select non-numeric
Regular expressions are overkill here.
#include <algorithm>
#include <iostream>
#include <iterator>
#include <string>
inline bool not_digit(char ch) {
return '0' <= ch && ch <= '9';
}
std::string remove_non_digits(const std::string& input) {
std::string result;
std::copy_if(input.begin(), input.end(),
std::back_inserter(result),
not_digit);
return result;
}
int main() {
std::string input = "1a2b3c";
std::string result = remove_non_digits(input);
std::cout << "Original: " << input << '\n';
std::cout << "Filtered: " << result << '\n';
return 0;
}
The accepted answer if fine for the specifics of the given sample.
But it will fail for a number such as "-12.34" (it would result in "1234").
(note how the sample could be negative numbers)
Then the regex should be:
(-|\+)?(\d)+(.(\d)+)*
explanation: (optional ( "-" or "+" )) with (a number, repeated 1 to n times) with (optionally end's with: ( a "." followed by (a number, repeated 1 to n times) )
A bit over-reaching, but I was looking for this and the page showed up first in my search, so I'm adding my answer for future searches.
Hello I been trying to find a way of finding a string of characters within two characters. How should I go about doing this in c++?
sdfgkjr$joeisawesome$sdfeids -> joeisawesome
EDIT: The other answer is looking for if a string exist within a string. I'm looking for a string within two characters and outputting the sting within the two chars. Thank you for looking PoX.
Okay, so when you say two characters, I'm assuming that you are referring to delimiters. In this case you would have to use String.find() to find the position of the delimiters. After finding the positions of the delimiters, you can can use String.substr(index1,index2-index1) to return the substring.
Example:
#include <iostream>
#include <string>
int main()
{
std::size_t index1,index2;
std::string myString = "sdfgkjr$joeisawesome$sdfeids";
std::string sub= "";
index1 = myString.find('$');
//string::npos is -1 if you are unaware
if(index1!=std::string::npos&& index1<myString.length()-1)
index2=myString.find('$',index1+1);
if(index2!=std::string::npos)
{
sub = myString.substr(index1+1,index2-index1);
}
std::cout<<sub; //outputs joeisawesome
}